Fastify (#9106)

* wip

* wip

* wip

* wip

* wip

* wip

* wip

* wip

* wip

* wip

* fix

* Update SignupApiService.ts

* wip

* wip

* Update ClientServerService.ts

* wip

* wip

* wip

* Update WellKnownServerService.ts

* wip

* wip

* update des

* wip

* Update ApiServerService.ts

* wip

* update deps

* Update WellKnownServerService.ts

* wip

* update deps

* Update ApiCallService.ts

* Update ApiCallService.ts

* Update ApiServerService.ts

30 files changed, 1017 insertions, 1032 deletions

diff --git a/packages/backend/package.json b/packages/backend/package.json
index 9e50d4d9fa..81e7888b84 100644
--- a/packages/backend/package.json
+++ b/packages/backend/package.json
@@ -21,20 +21,19 @@
 		"@tensorflow/tfjs-node": "4.1.0"
 	},
 	"dependencies": {
-		"@bull-board/api": "4.3.1",
-		"@bull-board/koa": "4.3.1",
-		"@bull-board/ui": "4.3.1",
 		"@discordapp/twemoji": "14.0.2",
-		"@elastic/elasticsearch": "7.17.0",
-		"@koa/cors": "3.3.0",
-		"@koa/multer": "3.0.0",
-		"@koa/router": "9.0.1",
+		"@fastify/accepts": "4.0.1",
+		"@fastify/cors": "8.2.0",
+		"@fastify/multipart": "7.3.0",
+		"@fastify/static": "6.5.0",
+		"@fastify/view": "7.1.2",
 		"@nestjs/common": "9.2.0",
 		"@nestjs/core": "9.2.0",
 		"@nestjs/testing": "9.2.0",
 		"@peertube/http-signature": "1.7.0",
 		"@sinonjs/fake-timers": "10.0.0",
 		"@syuilo/aiscript": "0.11.1",
+		"accepts": "^1.3.8",
 		"ajv": "8.11.2",
 		"archiver": "5.3.1",
 		"autobind-decorator": "2.4.0",
@@ -54,6 +53,7 @@
 		"date-fns": "2.29.3",
 		"deep-email-validator": "0.1.21",
 		"escape-regexp": "0.0.1",
+		"fastify": "4.10.0",
 		"feed": "4.2.2",
 		"file-type": "18.0.0",
 		"fluent-ffmpeg": "2.1.2",
@@ -69,20 +69,10 @@
 		"json5-loader": "4.0.1",
 		"jsonld": "8.1.0",
 		"jsrsasign": "10.6.1",
-		"koa": "2.13.4",
-		"koa-bodyparser": "4.3.0",
-		"koa-favicon": "2.1.0",
-		"koa-json-body": "5.3.0",
-		"koa-logger": "3.2.1",
-		"koa-mount": "4.0.0",
-		"koa-send": "5.0.1",
-		"koa-slow": "2.1.0",
-		"koa-views": "7.0.2",
 		"mfm-js": "0.23.0",
 		"mime-types": "2.1.35",
 		"misskey-js": "0.0.14",
 		"ms": "3.0.0-canary.1",
-		"multer": "1.4.4",
 		"nested-property": "4.0.0",
 		"node-fetch": "3.3.0",
 		"nodemailer": "6.8.0",
@@ -129,6 +119,7 @@
 		"ulid": "2.3.0",
 		"unzipper": "0.10.11",
 		"uuid": "9.0.0",
+		"vary": "1.1.2",
 		"web-push": "3.5.0",
 		"websocket": "1.0.34",
 		"ws": "8.11.0",
@@ -138,6 +129,7 @@
 		"@redocly/openapi-core": "1.0.0-beta.114",
 		"@swc/core": "1.3.20",
 		"@swc/jest": "0.2.23",
+		"@types/accepts": "1.3.5",
 		"@types/archiver": "5.3.1",
 		"@types/bcryptjs": "2.4.2",
 		"@types/bull": "4.10.0",
@@ -149,17 +141,6 @@
 		"@types/jsdom": "20.0.1",
 		"@types/jsonld": "1.5.8",
 		"@types/jsrsasign": "10.5.4",
-		"@types/koa": "2.13.5",
-		"@types/koa-bodyparser": "4.3.8",
-		"@types/koa-cors": "0.0.2",
-		"@types/koa-favicon": "2.0.21",
-		"@types/koa-logger": "3.1.2",
-		"@types/koa-mount": "4.0.1",
-		"@types/koa-send": "4.1.3",
-		"@types/koa-views": "7.0.0",
-		"@types/koa__cors": "3.3.0",
-		"@types/koa__multer": "2.0.4",
-		"@types/koa__router": "8.0.11",
 		"@types/mime-types": "2.1.1",
 		"@types/node": "18.11.9",
 		"@types/node-fetch": "3.0.3",
@@ -182,6 +163,7 @@
 		"@types/tmp": "0.2.3",
 		"@types/unzipper": "0.10.5",
 		"@types/uuid": "8.3.4",
+		"@types/vary": "1.1.0",
 		"@types/web-push": "3.3.2",
 		"@types/websocket": "1.0.5",
 		"@types/ws": "8.5.3",
diff --git a/packages/backend/src/@types/koa-json-body.d.ts b/packages/backend/src/@types/koa-json-body.d.ts
deleted file mode 100644
index 2971807d15..0000000000
--- a/packages/backend/src/@types/koa-json-body.d.ts
+++ /dev/null
@@ -1,15 +0,0 @@
-declare module 'koa-json-body' {
-	import type { Middleware } from 'koa';
-
-	interface IKoaJsonBodyOptions {
-		strict: boolean;
-		limit: string;
-		fallback: boolean;
-	}
-
-	function koaJsonBody(opt?: IKoaJsonBodyOptions): Middleware;
-
-	namespace koaJsonBody {} // Hack
-
-	export = koaJsonBody;
-}
diff --git a/packages/backend/src/@types/koa-slow.d.ts b/packages/backend/src/@types/koa-slow.d.ts
deleted file mode 100644
index d048822efe..0000000000
--- a/packages/backend/src/@types/koa-slow.d.ts
+++ /dev/null
@@ -1,14 +0,0 @@
-declare module 'koa-slow' {
-	import type { Middleware } from 'koa';
-
-	interface ISlowOptions {
-		url?: RegExp;
-		delay?: number;
-	}
-
-	function slow(options?: ISlowOptions): Middleware;
-
-	namespace slow {} // Hack
-
-	export = slow;
-}
diff --git a/packages/backend/src/boot/index.ts b/packages/backend/src/boot/index.ts
index fbf9e73e09..f4daf30690 100644
--- a/packages/backend/src/boot/index.ts
+++ b/packages/backend/src/boot/index.ts
@@ -52,6 +52,7 @@ if (!envOption.quiet) {
 process.on('uncaughtException', err => {
 	try {
 		logger.error(err);
+		console.trace(err);
 	} catch { }
 });
 
diff --git a/packages/backend/src/core/CaptchaService.ts b/packages/backend/src/core/CaptchaService.ts
index acfa7d5910..b2bc24ac2c 100644
--- a/packages/backend/src/core/CaptchaService.ts
+++ b/packages/backend/src/core/CaptchaService.ts
@@ -45,9 +45,13 @@ export class CaptchaService {
 		return await res.json() as CaptchaResponse;
 	}	
 	
-	public async verifyRecaptcha(secret: string, response: string): Promise<void> {
-		const result = await this.getCaptchaResponse('https://www.recaptcha.net/recaptcha/api/siteverify', secret, response).catch(e => {
-			throw `recaptcha-request-failed: ${e}`;
+	public async verifyRecaptcha(secret: string, response: string | null | undefined): Promise<void> {
+		if (response == null) {
+			throw 'recaptcha-failed: no response provided';
+		}
+
+		const result = await this.getCaptchaResponse('https://www.recaptcha.net/recaptcha/api/siteverify', secret, response).catch(err => {
+			throw `recaptcha-request-failed: ${err}`;
 		});
 
 		if (result.success !== true) {
@@ -56,9 +60,13 @@ export class CaptchaService {
 		}
 	}
 
-	public async verifyHcaptcha(secret: string, response: string): Promise<void> {
-		const result = await this.getCaptchaResponse('https://hcaptcha.com/siteverify', secret, response).catch(e => {
-			throw `hcaptcha-request-failed: ${e}`;
+	public async verifyHcaptcha(secret: string, response: string | null | undefined): Promise<void> {
+		if (response == null) {
+			throw 'hcaptcha-failed: no response provided';
+		}
+
+		const result = await this.getCaptchaResponse('https://hcaptcha.com/siteverify', secret, response).catch(err => {
+			throw `hcaptcha-request-failed: ${err}`;
 		});
 
 		if (result.success !== true) {
@@ -67,9 +75,13 @@ export class CaptchaService {
 		}
 	}
 
-	public async verifyTurnstile(secret: string, response: string): Promise<void> {
-		const result = await this.getCaptchaResponse('https://challenges.cloudflare.com/turnstile/v0/siteverify', secret, response).catch(e => {
-			throw `turnstile-request-failed: ${e}`;
+	public async verifyTurnstile(secret: string, response: string | null | undefined): Promise<void> {
+		if (response == null) {
+			throw 'turnstile-failed: no response provided';
+		}
+	
+		const result = await this.getCaptchaResponse('https://challenges.cloudflare.com/turnstile/v0/siteverify', secret, response).catch(err => {
+			throw `turnstile-request-failed: ${err}`;
 		});
 
 		if (result.success !== true) {
diff --git a/packages/backend/src/core/remote/activitypub/ApRendererService.ts b/packages/backend/src/core/remote/activitypub/ApRendererService.ts
index 38850fd127..38a92567c3 100644
--- a/packages/backend/src/core/remote/activitypub/ApRendererService.ts
+++ b/packages/backend/src/core/remote/activitypub/ApRendererService.ts
@@ -674,7 +674,7 @@ export class ApRendererService {
 	 * @param last URL of last page (optional)
 	 * @param orderedItems attached objects (optional)
 	 */
-	public renderOrderedCollection(id: string | null, totalItems: any, first?: string, last?: string, orderedItems?: Record<string, unknown>[]) {
+	public renderOrderedCollection(id: string | null, totalItems: any, first?: string, last?: string, orderedItems?: IObject[]) {
 		const page: any = {
 			id,
 			type: 'OrderedCollection',
diff --git a/packages/backend/src/env.ts b/packages/backend/src/env.ts
index 1b678edc44..d7c8304b47 100644
--- a/packages/backend/src/env.ts
+++ b/packages/backend/src/env.ts
@@ -6,7 +6,6 @@ const envOption = {
 	verbose: false,
 	withLogTime: false,
 	quiet: false,
-	slow: false,
 };
 
 for (const key of Object.keys(envOption) as (keyof typeof envOption)[]) {
diff --git a/packages/backend/src/misc/create-temp.ts b/packages/backend/src/misc/create-temp.ts
index fa88769de0..429977669e 100644
--- a/packages/backend/src/misc/create-temp.ts
+++ b/packages/backend/src/misc/create-temp.ts
@@ -18,7 +18,7 @@ export function createTempDir(): Promise<[string, () => void]> {
 			(e, path, cleanup) => {
 				if (e) return rej(e);
 				res([path, cleanup]);
-			}
+			},
 		);
 	});
 }
diff --git a/packages/backend/src/misc/fastify-reply-error.ts b/packages/backend/src/misc/fastify-reply-error.ts
new file mode 100644
index 0000000000..4e987175e2
--- /dev/null
+++ b/packages/backend/src/misc/fastify-reply-error.ts
@@ -0,0 +1,11 @@
+// https://www.fastify.io/docs/latest/Reference/Reply/#async-await-and-promises
+export class FastifyReplyError extends Error {
+	public message: string;
+	public statusCode: number;
+
+	constructor(statusCode: number, message: string) {
+		super(message);
+		this.message = message;
+		this.statusCode = statusCode;
+	}
+}
diff --git a/packages/backend/src/server/ActivityPubServerService.ts b/packages/backend/src/server/ActivityPubServerService.ts
index 2e7bd4dcb2..9689a623fd 100644
--- a/packages/backend/src/server/ActivityPubServerService.ts
+++ b/packages/backend/src/server/ActivityPubServerService.ts
@@ -1,8 +1,9 @@
 import { Inject, Injectable } from '@nestjs/common';
-import Router from '@koa/router';
-import json from 'koa-json-body';
+import { FastifyInstance, FastifyRequest, FastifyReply, FastifyPluginOptions } from 'fastify';
+import fastifyAccepts from '@fastify/accepts';
 import httpSignature from '@peertube/http-signature';
 import { Brackets, In, IsNull, LessThan, Not } from 'typeorm';
+import accepts from 'accepts';
 import { DI } from '@/di-symbols.js';
 import type { FollowingsRepository, NotesRepository, EmojisRepository, NoteReactionsRepository, UserProfilesRepository, UserNotePiningsRepository, UsersRepository } from '@/models/index.js';
 import * as url from '@/misc/prelude/url.js';
@@ -56,14 +57,15 @@ export class ActivityPubServerService {
 		private userKeypairStoreService: UserKeypairStoreService,
 		private queryService: QueryService,
 	) {
+		this.createServer = this.createServer.bind(this);
 	}
 
-	private setResponseType(ctx: Router.RouterContext) {
-		const accept = ctx.accepts(ACTIVITY_JSON, LD_JSON);
+	private setResponseType(request: FastifyRequest, reply: FastifyReply): void {
+		const accept = request.accepts().type([ACTIVITY_JSON, LD_JSON]);
 		if (accept === LD_JSON) {
-			ctx.response.type = LD_JSON;
+			reply.type(LD_JSON);
 		} else {
-			ctx.response.type = ACTIVITY_JSON;
+			reply.type(ACTIVITY_JSON);
 		}
 	}
 
@@ -80,31 +82,34 @@ export class ActivityPubServerService {
 		return this.apRendererService.renderCreate(await this.apRendererService.renderNote(note, false), note);
 	}
 
-	private inbox(ctx: Router.RouterContext) {
+	private inbox(request: FastifyRequest, reply: FastifyReply) {
 		let signature;
 
 		try {
-			signature = httpSignature.parseRequest(ctx.req, { 'headers': [] });
+			signature = httpSignature.parseRequest(request.raw, { 'headers': [] });
 		} catch (e) {
-			ctx.status = 401;
+			reply.code(401);
 			return;
 		}
 
-		this.queueService.inbox(ctx.request.body, signature);
+		this.queueService.inbox(request.body, signature);
 
-		ctx.status = 202;
+		reply.code(202);
 	}
 
-	private async followers(ctx: Router.RouterContext) {
-		const userId = ctx.params.user;
+	private async followers(
+		request: FastifyRequest<{ Params: { user: string; }; Querystring: { cursor?: string; page?: string; }; }>,
+		reply: FastifyReply,
+	) {
+		const userId = request.params.user;
 
-		const cursor = ctx.request.query.cursor;
+		const cursor = request.query.cursor;
 		if (cursor != null && typeof cursor !== 'string') {
-			ctx.status = 400;
+			reply.code(400);
 			return;
 		}
 
-		const page = ctx.request.query.page === 'true';
+		const page = request.query.page === 'true';
 
 		const user = await this.usersRepository.findOneBy({
 			id: userId,
@@ -112,7 +117,7 @@ export class ActivityPubServerService {
 		});
 
 		if (user == null) {
-			ctx.status = 404;
+			reply.code(404);
 			return;
 		}
 
@@ -120,12 +125,12 @@ export class ActivityPubServerService {
 		const profile = await this.userProfilesRepository.findOneByOrFail({ userId: user.id });
 
 		if (profile.ffVisibility === 'private') {
-			ctx.status = 403;
-			ctx.set('Cache-Control', 'public, max-age=30');
+			reply.code(403);
+			reply.header('Cache-Control', 'public, max-age=30');
 			return;
 		} else if (profile.ffVisibility === 'followers') {
-			ctx.status = 403;
-			ctx.set('Cache-Control', 'public, max-age=30');
+			reply.code(403);
+			reply.header('Cache-Control', 'public, max-age=30');
 			return;
 		}
 		//#endregion
@@ -168,27 +173,30 @@ export class ActivityPubServerService {
 				})}` : undefined,
 			);
 
-			ctx.body = this.apRendererService.renderActivity(rendered);
-			this.setResponseType(ctx);
+			this.setResponseType(request, reply);
+			return (this.apRendererService.renderActivity(rendered));
 		} else {
 			// index page
 			const rendered = this.apRendererService.renderOrderedCollection(partOf, user.followersCount, `${partOf}?page=true`);
-			ctx.body = this.apRendererService.renderActivity(rendered);
-			ctx.set('Cache-Control', 'public, max-age=180');
-			this.setResponseType(ctx);
+			reply.header('Cache-Control', 'public, max-age=180');
+			this.setResponseType(request, reply);
+			return (this.apRendererService.renderActivity(rendered));
 		}
 	}
 
-	private async following(ctx: Router.RouterContext) {
-		const userId = ctx.params.user;
+	private async following(
+		request: FastifyRequest<{ Params: { user: string; }; Querystring: { cursor?: string; page?: string; }; }>,
+		reply: FastifyReply,
+	) {
+		const userId = request.params.user;
 
-		const cursor = ctx.request.query.cursor;
+		const cursor = request.query.cursor;
 		if (cursor != null && typeof cursor !== 'string') {
-			ctx.status = 400;
+			reply.code(400);
 			return;
 		}
 	
-		const page = ctx.request.query.page === 'true';
+		const page = request.query.page === 'true';
 	
 		const user = await this.usersRepository.findOneBy({
 			id: userId,
@@ -196,7 +204,7 @@ export class ActivityPubServerService {
 		});
 	
 		if (user == null) {
-			ctx.status = 404;
+			reply.code(404);
 			return;
 		}
 	
@@ -204,12 +212,12 @@ export class ActivityPubServerService {
 		const profile = await this.userProfilesRepository.findOneByOrFail({ userId: user.id });
 	
 		if (profile.ffVisibility === 'private') {
-			ctx.status = 403;
-			ctx.set('Cache-Control', 'public, max-age=30');
+			reply.code(403);
+			reply.header('Cache-Control', 'public, max-age=30');
 			return;
 		} else if (profile.ffVisibility === 'followers') {
-			ctx.status = 403;
-			ctx.set('Cache-Control', 'public, max-age=30');
+			reply.code(403);
+			reply.header('Cache-Control', 'public, max-age=30');
 			return;
 		}
 		//#endregion
@@ -252,19 +260,19 @@ export class ActivityPubServerService {
 				})}` : undefined,
 			);
 	
-			ctx.body = this.apRendererService.renderActivity(rendered);
-			this.setResponseType(ctx);
+			this.setResponseType(request, reply);
+			return (this.apRendererService.renderActivity(rendered));
 		} else {
 			// index page
 			const rendered = this.apRendererService.renderOrderedCollection(partOf, user.followingCount, `${partOf}?page=true`);
-			ctx.body = this.apRendererService.renderActivity(rendered);
-			ctx.set('Cache-Control', 'public, max-age=180');
-			this.setResponseType(ctx);
+			reply.header('Cache-Control', 'public, max-age=180');
+			this.setResponseType(request, reply);
+			return (this.apRendererService.renderActivity(rendered));
 		}
 	}
 
-	private async featured(ctx: Router.RouterContext) {
-		const userId = ctx.params.user;
+	private async featured(request: FastifyRequest<{ Params: { user: string; }; }>, reply: FastifyReply) {
+		const userId = request.params.user;
 
 		const user = await this.usersRepository.findOneBy({
 			id: userId,
@@ -272,7 +280,7 @@ export class ActivityPubServerService {
 		});
 
 		if (user == null) {
-			ctx.status = 404;
+			reply.code(404);
 			return;
 		}
 
@@ -291,30 +299,36 @@ export class ActivityPubServerService {
 			renderedNotes.length, undefined, undefined, renderedNotes,
 		);
 
-		ctx.body = this.apRendererService.renderActivity(rendered);
-		ctx.set('Cache-Control', 'public, max-age=180');
-		this.setResponseType(ctx);
+		reply.header('Cache-Control', 'public, max-age=180');
+		this.setResponseType(request, reply);
+		return (this.apRendererService.renderActivity(rendered));
 	}
 
-	private async outbox(ctx: Router.RouterContext) {
-		const userId = ctx.params.user;
+	private async outbox(
+		request: FastifyRequest<{
+			Params: { user: string; };
+			Querystring: { since_id?: string; until_id?: string; page?: string; };
+		}>,
+		reply: FastifyReply,
+	) {
+		const userId = request.params.user;
 
-		const sinceId = ctx.request.query.since_id;
+		const sinceId = request.query.since_id;
 		if (sinceId != null && typeof sinceId !== 'string') {
-			ctx.status = 400;
+			reply.code(400);
 			return;
 		}
 	
-		const untilId = ctx.request.query.until_id;
+		const untilId = request.query.until_id;
 		if (untilId != null && typeof untilId !== 'string') {
-			ctx.status = 400;
+			reply.code(400);
 			return;
 		}
 	
-		const page = ctx.request.query.page === 'true';
+		const page = request.query.page === 'true';
 	
 		if (countIf(x => x != null, [sinceId, untilId]) > 1) {
-			ctx.status = 400;
+			reply.code(400);
 			return;
 		}
 	
@@ -324,7 +338,7 @@ export class ActivityPubServerService {
 		});
 	
 		if (user == null) {
-			ctx.status = 404;
+			reply.code(404);
 			return;
 		}
 	
@@ -362,110 +376,130 @@ export class ActivityPubServerService {
 				})}` : undefined,
 			);
 	
-			ctx.body = this.apRendererService.renderActivity(rendered);
-			this.setResponseType(ctx);
+			this.setResponseType(request, reply);
+			return (this.apRendererService.renderActivity(rendered));
 		} else {
 			// index page
 			const rendered = this.apRendererService.renderOrderedCollection(partOf, user.notesCount,
 				`${partOf}?page=true`,
 				`${partOf}?page=true&since_id=000000000000000000000000`,
 			);
-			ctx.body = this.apRendererService.renderActivity(rendered);
-			ctx.set('Cache-Control', 'public, max-age=180');
-			this.setResponseType(ctx);
+			reply.header('Cache-Control', 'public, max-age=180');
+			this.setResponseType(request, reply);
+			return (this.apRendererService.renderActivity(rendered));
 		}
 	}
 
-	private async userInfo(ctx: Router.RouterContext, user: User | null) {
+	private async userInfo(request: FastifyRequest, reply: FastifyReply, user: User | null) {
 		if (user == null) {
-			ctx.status = 404;
+			reply.code(404);
 			return;
 		}
 
-		ctx.body = this.apRendererService.renderActivity(await this.apRendererService.renderPerson(user as ILocalUser));
-		ctx.set('Cache-Control', 'public, max-age=180');
-		this.setResponseType(ctx);
+		reply.header('Cache-Control', 'public, max-age=180');
+		this.setResponseType(request, reply);
+		return (this.apRendererService.renderActivity(await this.apRendererService.renderPerson(user as ILocalUser)));
 	}
 
-	public createRouter() {
-		// Init router
-		const router = new Router();
+	public createServer(fastify: FastifyInstance, options: FastifyPluginOptions, done: (err?: Error) => void) {
+		fastify.addConstraintStrategy({
+			name: 'apOrHtml',
+			storage() {
+				const store = {};
+				return {
+					get(key) {
+						return store[key] ?? null;
+					},
+					set(key, value) {
+						store[key] = value;
+					},
+				};
+			},
+			deriveConstraint(request, ctx) {
+				const accepted = accepts(request).type(['html', ACTIVITY_JSON, LD_JSON]);
+				const isAp = typeof accepted === 'string' && !accepted.match(/html/);
+				return isAp ? 'ap' : 'html';
+			},
+		});
 
-		//#region Routing
-		function isActivityPubReq(ctx: Router.RouterContext) {
-			ctx.response.vary('Accept');
-			const accepted = ctx.accepts('html', ACTIVITY_JSON, LD_JSON);
-			return typeof accepted === 'string' && !accepted.match(/html/);
-		}
+		fastify.register(fastifyAccepts);
 
+		//#region Routing
 		// inbox
-		router.post('/inbox', json(), ctx => this.inbox(ctx));
-		router.post('/users/:user/inbox', json(), ctx => this.inbox(ctx));
+		fastify.post('/inbox', async (request, reply) => await this.inbox(request, reply));
+		fastify.post('/users/:user/inbox', async (request, reply) => await this.inbox(request, reply));
 
 		// note
-		router.get('/notes/:note', async (ctx, next) => {
-			if (!isActivityPubReq(ctx)) return await next();
-
+		fastify.get<{ Params: { note: string; } }>('/notes/:note', { constraints: { apOrHtml: 'ap' } }, async (request, reply) => {
 			const note = await this.notesRepository.findOneBy({
-				id: ctx.params.note,
+				id: request.params.note,
 				visibility: In(['public' as const, 'home' as const]),
 				localOnly: false,
 			});
 
 			if (note == null) {
-				ctx.status = 404;
+				reply.code(404);
 				return;
 			}
 
 			// リモートだったらリダイレクト
 			if (note.userHost != null) {
 				if (note.uri == null || this.utilityService.isSelfHost(note.userHost)) {
-					ctx.status = 500;
+					reply.code(500);
 					return;
 				}
-				ctx.redirect(note.uri);
+				reply.redirect(note.uri);
 				return;
 			}
 
-			ctx.body = this.apRendererService.renderActivity(await this.apRendererService.renderNote(note, false));
-			ctx.set('Cache-Control', 'public, max-age=180');
-			this.setResponseType(ctx);
+			reply.header('Cache-Control', 'public, max-age=180');
+			this.setResponseType(request, reply);
+			return (this.apRendererService.renderActivity(await this.apRendererService.renderNote(note, false)));
 		});
 
 		// note activity
-		router.get('/notes/:note/activity', async ctx => {
+		fastify.get<{ Params: { note: string; } }>('/notes/:note/activity', async (request, reply) => {
 			const note = await this.notesRepository.findOneBy({
-				id: ctx.params.note,
+				id: request.params.note,
 				userHost: IsNull(),
 				visibility: In(['public' as const, 'home' as const]),
 				localOnly: false,
 			});
 
 			if (note == null) {
-				ctx.status = 404;
+				reply.code(404);
 				return;
 			}
 
-			ctx.body = this.apRendererService.renderActivity(await this.packActivity(note));
-			ctx.set('Cache-Control', 'public, max-age=180');
-			this.setResponseType(ctx);
+			reply.header('Cache-Control', 'public, max-age=180');
+			this.setResponseType(request, reply);
+			return (this.apRendererService.renderActivity(await this.packActivity(note)));
 		});
 
 		// outbox
-		router.get('/users/:user/outbox', (ctx) => this.outbox(ctx));
+		fastify.get<{
+			Params: { user: string; };
+			Querystring: { since_id?: string; until_id?: string; page?: string; };
+		}>('/users/:user/outbox', async (request, reply) => await this.outbox(request, reply));
 
 		// followers
-		router.get('/users/:user/followers', (ctx) => this.followers(ctx));
+		fastify.get<{
+			Params: { user: string; };
+			Querystring: { cursor?: string; page?: string; };
+		}>('/users/:user/followers', async (request, reply) => await this.followers(request, reply));
 
 		// following
-		router.get('/users/:user/following', (ctx) => this.following(ctx));
+		fastify.get<{
+			Params: { user: string; };
+			Querystring: { cursor?: string; page?: string; };
+		}>('/users/:user/following', async (request, reply) => await this.following(request, reply));
 
 		// featured
-		router.get('/users/:user/collections/featured', (ctx) => this.featured(ctx));
+		fastify.get<{ Params: { user: string; }; }>('/users/:user/collections/featured', async (request, reply) => await this.featured(request, reply));
 
 		// publickey
-		router.get('/users/:user/publickey', async ctx => {
-			const userId = ctx.params.user;
+		fastify.get<{ Params: { user: string; } }>('/users/:user/publickey', async (request, reply) => {
+			const userId = request.params.user;
 
 			const user = await this.usersRepository.findOneBy({
 				id: userId,
@@ -473,25 +507,23 @@ export class ActivityPubServerService {
 			});
 
 			if (user == null) {
-				ctx.status = 404;
+				reply.code(404);
 				return;
 			}
 
 			const keypair = await this.userKeypairStoreService.getUserKeypair(user.id);
 
 			if (this.userEntityService.isLocalUser(user)) {
-				ctx.body = this.apRendererService.renderActivity(this.apRendererService.renderKey(user, keypair));
-				ctx.set('Cache-Control', 'public, max-age=180');
-				this.setResponseType(ctx);
+				reply.header('Cache-Control', 'public, max-age=180');
+				this.setResponseType(request, reply);
+				return (this.apRendererService.renderActivity(this.apRendererService.renderKey(user, keypair)));
 			} else {
-				ctx.status = 400;
+				reply.code(400);
 			}
 		});
 
-		router.get('/users/:user', async (ctx, next) => {
-			if (!isActivityPubReq(ctx)) return await next();
-
-			const userId = ctx.params.user;
+		fastify.get<{ Params: { user: string; } }>('/users/:user', { constraints: { apOrHtml: 'ap' } }, async (request, reply) => {
+			const userId = request.params.user;
 
 			const user = await this.usersRepository.findOneBy({
 				id: userId,
@@ -499,86 +531,84 @@ export class ActivityPubServerService {
 				isSuspended: false,
 			});
 
-			await this.userInfo(ctx, user);
+			return await this.userInfo(request, reply, user);
 		});
 
-		router.get('/@:user', async (ctx, next) => {
-			if (!isActivityPubReq(ctx)) return await next();
-
+		fastify.get<{ Params: { user: string; } }>('/@:user', { constraints: { apOrHtml: 'ap' } }, async (request, reply) => {
 			const user = await this.usersRepository.findOneBy({
-				usernameLower: ctx.params.user.toLowerCase(),
+				usernameLower: request.params.user.toLowerCase(),
 				host: IsNull(),
 				isSuspended: false,
 			});
 
-			await this.userInfo(ctx, user);
+			return await this.userInfo(request, reply, user);
 		});
 		//#endregion
 
 		// emoji
-		router.get('/emojis/:emoji', async ctx => {
+		fastify.get<{ Params: { emoji: string; } }>('/emojis/:emoji', async (request, reply) => {
 			const emoji = await this.emojisRepository.findOneBy({
 				host: IsNull(),
-				name: ctx.params.emoji,
+				name: request.params.emoji,
 			});
 
 			if (emoji == null) {
-				ctx.status = 404;
+				reply.code(404);
 				return;
 			}
 
-			ctx.body = this.apRendererService.renderActivity(await this.apRendererService.renderEmoji(emoji));
-			ctx.set('Cache-Control', 'public, max-age=180');
-			this.setResponseType(ctx);
+			reply.header('Cache-Control', 'public, max-age=180');
+			this.setResponseType(request, reply);
+			return (this.apRendererService.renderActivity(await this.apRendererService.renderEmoji(emoji)));
 		});
 
 		// like
-		router.get('/likes/:like', async ctx => {
-			const reaction = await this.noteReactionsRepository.findOneBy({ id: ctx.params.like });
+		fastify.get<{ Params: { like: string; } }>('/likes/:like', async (request, reply) => {
+			const reaction = await this.noteReactionsRepository.findOneBy({ id: request.params.like });
 
 			if (reaction == null) {
-				ctx.status = 404;
+				reply.code(404);
 				return;
 			}
 
 			const note = await this.notesRepository.findOneBy({ id: reaction.noteId });
 
 			if (note == null) {
-				ctx.status = 404;
+				reply.code(404);
 				return;
 			}
 
-			ctx.body = this.apRendererService.renderActivity(await this.apRendererService.renderLike(reaction, note));
-			ctx.set('Cache-Control', 'public, max-age=180');
-			this.setResponseType(ctx);
+			reply.header('Cache-Control', 'public, max-age=180');
+			this.setResponseType(request, reply);
+			return (this.apRendererService.renderActivity(await this.apRendererService.renderLike(reaction, note)));
 		});
 
 		// follow
-		router.get('/follows/:follower/:followee', async ctx => {
+		fastify.get<{ Params: { follower: string; followee: string; } }>('/follows/:follower/:followee', async (request, reply) => {
 			// This may be used before the follow is completed, so we do not
 			// check if the following exists.
 
 			const [follower, followee] = await Promise.all([
 				this.usersRepository.findOneBy({
-					id: ctx.params.follower,
+					id: request.params.follower,
 					host: IsNull(),
 				}),
 				this.usersRepository.findOneBy({
-					id: ctx.params.followee,
+					id: request.params.followee,
 					host: Not(IsNull()),
 				}),
 			]);
 
 			if (follower == null || followee == null) {
-				ctx.status = 404;
+				reply.code(404);
 				return;
 			}
 
-			ctx.body = this.apRendererService.renderActivity(this.apRendererService.renderFollow(follower, followee));
-			ctx.set('Cache-Control', 'public, max-age=180');
-			this.setResponseType(ctx);
+			reply.header('Cache-Control', 'public, max-age=180');
+			this.setResponseType(request, reply);
+			return (this.apRendererService.renderActivity(this.apRendererService.renderFollow(follower, followee)));
 		});
 
-		return router;
+		done();
 	}
 }
diff --git a/packages/backend/src/server/FileServerService.ts b/packages/backend/src/server/FileServerService.ts
index dc073e34ac..088e780d69 100644
--- a/packages/backend/src/server/FileServerService.ts
+++ b/packages/backend/src/server/FileServerService.ts
@@ -2,10 +2,8 @@ import * as fs from 'node:fs';
 import { fileURLToPath } from 'node:url';
 import { dirname } from 'node:path';
 import { Inject, Injectable } from '@nestjs/common';
-import Koa from 'koa';
-import cors from '@koa/cors';
-import Router from '@koa/router';
-import send from 'koa-send';
+import { FastifyInstance, FastifyRequest, FastifyReply, FastifyPluginOptions } from 'fastify';
+import fastifyStatic from '@fastify/static';
 import rename from 'rename';
 import type { Config } from '@/config.js';
 import type { DriveFilesRepository } from '@/models/index.js';
@@ -46,45 +44,44 @@ export class FileServerService {
 		private loggerService: LoggerService,
 	) {
 		this.logger = this.loggerService.getLogger('server', 'gray', false);
+
+		this.createServer = this.createServer.bind(this);
 	}
 
-	public commonReadableHandlerGenerator(ctx: Koa.Context) {
-		return (e: Error): void => {
-			this.logger.error(e);
-			ctx.status = 500;
-			ctx.set('Cache-Control', 'max-age=300');
+	public commonReadableHandlerGenerator(reply: FastifyReply) {
+		return (err: Error): void => {
+			this.logger.error(err);
+			reply.code(500);
+			reply.header('Cache-Control', 'max-age=300');
 		};
 	}
 	
-	public createServer() {
-		const app = new Koa();
-		app.use(cors());
-		app.use(async (ctx, next) => {
-			ctx.set('Content-Security-Policy', 'default-src \'none\'; img-src \'self\'; media-src \'self\'; style-src \'unsafe-inline\'');
-			await next();
+	public createServer(fastify: FastifyInstance, options: FastifyPluginOptions, done: (err?: Error) => void) {
+		fastify.addHook('onRequest', (request, reply, done) => {
+			reply.header('Content-Security-Policy', 'default-src \'none\'; img-src \'self\'; media-src \'self\'; style-src \'unsafe-inline\'');
+			done();
 		});
 
-		// Init router
-		const router = new Router();
+		fastify.register(fastifyStatic, {
+			root: _dirname,
+			serve: false,
+		});
 
-		router.get('/app-default.jpg', ctx => {
+		fastify.get('/app-default.jpg', (request, reply) => {
 			const file = fs.createReadStream(`${_dirname}/assets/dummy.png`);
-			ctx.body = file;
-			ctx.set('Content-Type', 'image/jpeg');
-			ctx.set('Cache-Control', 'max-age=31536000, immutable');
+			reply.header('Content-Type', 'image/jpeg');
+			reply.header('Cache-Control', 'max-age=31536000, immutable');
+			return reply.send(file);
 		});
 
-		router.get('/:key', ctx => this.sendDriveFile(ctx));
-		router.get('/:key/(.*)', ctx => this.sendDriveFile(ctx));
-
-		// Register router
-		app.use(router.routes());
+		fastify.get<{ Params: { key: string; } }>('/:key', async (request, reply) => await this.sendDriveFile(request, reply));
+		fastify.get<{ Params: { key: string; } }>('/:key/*', async (request, reply) => await this.sendDriveFile(request, reply));
 
-		return app;
+		done();
 	}
 
-	private async sendDriveFile(ctx: Koa.Context) {
-		const key = ctx.params.key;
+	private async sendDriveFile(request: FastifyRequest<{ Params: { key: string; } }>, reply: FastifyReply) {
+		const key = request.params.key;
 
 		// Fetch drive file
 		const file = await this.driveFilesRepository.createQueryBuilder('file')
@@ -94,10 +91,9 @@ export class FileServerService {
 			.getOne();
 
 		if (file == null) {
-			ctx.status = 404;
-			ctx.set('Cache-Control', 'max-age=86400');
-			await send(ctx as any, '/dummy.png', { root: assets });
-			return;
+			reply.code(404);
+			reply.header('Cache-Control', 'max-age=86400');
+			return reply.sendFile('/dummy.png', assets);
 		}
 
 		const isThumbnail = file.thumbnailAccessKey === key;
@@ -135,18 +131,18 @@ export class FileServerService {
 					};
 
 					const image = await convertFile();
-					ctx.body = image.data;
-					ctx.set('Content-Type', FILE_TYPE_BROWSERSAFE.includes(image.type) ? image.type : 'application/octet-stream');
-					ctx.set('Cache-Control', 'max-age=31536000, immutable');
+					reply.header('Content-Type', FILE_TYPE_BROWSERSAFE.includes(image.type) ? image.type : 'application/octet-stream');
+					reply.header('Cache-Control', 'max-age=31536000, immutable');
+					return image.data;
 				} catch (err) {
 					this.logger.error(`${err}`);
 
 					if (err instanceof StatusError && err.isClientError) {
-						ctx.status = err.statusCode;
-						ctx.set('Cache-Control', 'max-age=86400');
+						reply.code(err.statusCode);
+						reply.header('Cache-Control', 'max-age=86400');
 					} else {
-						ctx.status = 500;
-						ctx.set('Cache-Control', 'max-age=300');
+						reply.code(500);
+						reply.header('Cache-Control', 'max-age=300');
 					}
 				} finally {
 					cleanup();
@@ -154,8 +150,8 @@ export class FileServerService {
 				return;
 			}
 
-			ctx.status = 204;
-			ctx.set('Cache-Control', 'max-age=86400');
+			reply.code(204);
+			reply.header('Cache-Control', 'max-age=86400');
 			return;
 		}
 
@@ -166,18 +162,17 @@ export class FileServerService {
 				extname: ext ? `.${ext}` : undefined,
 			}).toString();
 
-			ctx.body = this.internalStorageService.read(key);
-			ctx.set('Content-Type', FILE_TYPE_BROWSERSAFE.includes(mime) ? mime : 'application/octet-stream');
-			ctx.set('Cache-Control', 'max-age=31536000, immutable');
-			ctx.set('Content-Disposition', contentDisposition('inline', filename));
+			reply.header('Content-Type', FILE_TYPE_BROWSERSAFE.includes(mime) ? mime : 'application/octet-stream');
+			reply.header('Cache-Control', 'max-age=31536000, immutable');
+			reply.header('Content-Disposition', contentDisposition('inline', filename));
+			return this.internalStorageService.read(key);
 		} else {
 			const readable = this.internalStorageService.read(file.accessKey!);
-			readable.on('error', this.commonReadableHandlerGenerator(ctx));
-			ctx.body = readable;
-			ctx.set('Content-Type', FILE_TYPE_BROWSERSAFE.includes(file.type) ? file.type : 'application/octet-stream');
-			ctx.set('Cache-Control', 'max-age=31536000, immutable');
-			ctx.set('Content-Disposition', contentDisposition('inline', file.name));
+			readable.on('error', this.commonReadableHandlerGenerator(reply));
+			reply.header('Content-Type', FILE_TYPE_BROWSERSAFE.includes(file.type) ? file.type : 'application/octet-stream');
+			reply.header('Cache-Control', 'max-age=31536000, immutable');
+			reply.header('Content-Disposition', contentDisposition('inline', file.name));
+			return readable;
 		}
 	}
 }
-
diff --git a/packages/backend/src/server/MediaProxyServerService.ts b/packages/backend/src/server/MediaProxyServerService.ts
index 31841d39df..4d7bbdf599 100644
--- a/packages/backend/src/server/MediaProxyServerService.ts
+++ b/packages/backend/src/server/MediaProxyServerService.ts
@@ -1,8 +1,6 @@
 import * as fs from 'node:fs';
 import { Inject, Injectable } from '@nestjs/common';
-import Koa from 'koa';
-import cors from '@koa/cors';
-import Router from '@koa/router';
+import { FastifyInstance, FastifyPluginOptions, FastifyReply, FastifyRequest } from 'fastify';
 import sharp from 'sharp';
 import { DI } from '@/di-symbols.js';
 import type { Config } from '@/config.js';
@@ -31,32 +29,29 @@ export class MediaProxyServerService {
 		private loggerService: LoggerService,
 	) {
 		this.logger = this.loggerService.getLogger('server', 'gray', false);
+
+		this.createServer = this.createServer.bind(this);
 	}
 
-	public createServer() {
-		const app = new Koa();
-		app.use(cors());
-		app.use(async (ctx, next) => {
-			ctx.set('Content-Security-Policy', 'default-src \'none\'; img-src \'self\'; media-src \'self\'; style-src \'unsafe-inline\'');
-			await next();
+	public createServer(fastify: FastifyInstance, options: FastifyPluginOptions, done: (err?: Error) => void) {
+		fastify.addHook('onRequest', (request, reply, done) => {
+			reply.header('Content-Security-Policy', 'default-src \'none\'; img-src \'self\'; media-src \'self\'; style-src \'unsafe-inline\'');
+			done();
 		});
 
-		// Init router
-		const router = new Router();
-
-		router.get('/:url*', ctx => this.handler(ctx));
-
-		// Register router
-		app.use(router.routes());
+		fastify.get<{
+			Params: { url: string; };
+			Querystring: { url?: string; };
+		}>('/:url*', async (request, reply) => await this.handler(request, reply));
 
-		return app;
+		done();
 	}
 
-	private async handler(ctx: Koa.Context) {
-		const url = 'url' in ctx.query ? ctx.query.url : 'https://' + ctx.params.url;
+	private async handler(request: FastifyRequest<{ Params: { url: string; }; Querystring: { url?: string; }; }>, reply: FastifyReply) {
+		const url = 'url' in request.query ? request.query.url : 'https://' + request.params.url;
 	
 		if (typeof url !== 'string') {
-			ctx.status = 400;
+			reply.code(400);
 			return;
 		}
 	
@@ -71,11 +66,11 @@ export class MediaProxyServerService {
 	
 			let image: IImage;
 	
-			if ('static' in ctx.query && isConvertibleImage) {
+			if ('static' in request.query && isConvertibleImage) {
 				image = await this.imageProcessingService.convertToWebp(path, 498, 280);
-			} else if ('preview' in ctx.query && isConvertibleImage) {
+			} else if ('preview' in request.query && isConvertibleImage) {
 				image = await this.imageProcessingService.convertToWebp(path, 200, 200);
-			} else if ('badge' in ctx.query) {
+			} else if ('badge' in request.query) {
 				if (!isConvertibleImage) {
 					// 画像でないなら404でお茶を濁す
 					throw new StatusError('Unexpected mime', 404);
@@ -122,16 +117,16 @@ export class MediaProxyServerService {
 				};
 			}
 	
-			ctx.set('Content-Type', image.type);
-			ctx.set('Cache-Control', 'max-age=31536000, immutable');
-			ctx.body = image.data;
+			reply.header('Content-Type', image.type);
+			reply.header('Cache-Control', 'max-age=31536000, immutable');
+			return image.data;
 		} catch (err) {
 			this.logger.error(`${err}`);
 	
 			if (err instanceof StatusError && (err.statusCode === 302 || err.isClientError)) {
-				ctx.status = err.statusCode;
+				reply.code(err.statusCode);
 			} else {
-				ctx.status = 500;
+				reply.code(500);
 			}
 		} finally {
 			cleanup();
diff --git a/packages/backend/src/server/NodeinfoServerService.ts b/packages/backend/src/server/NodeinfoServerService.ts
index ef4ec74a35..b85925f53e 100644
--- a/packages/backend/src/server/NodeinfoServerService.ts
+++ b/packages/backend/src/server/NodeinfoServerService.ts
@@ -1,5 +1,5 @@
 import { Inject, Injectable } from '@nestjs/common';
-import Router from '@koa/router';
+import { FastifyInstance, FastifyPluginOptions, FastifyReply, FastifyRequest } from 'fastify';
 import { IsNull, MoreThan } from 'typeorm';
 import { DI } from '@/di-symbols.js';
 import type { NotesRepository, UsersRepository } from '@/models/index.js';
@@ -27,6 +27,7 @@ export class NodeinfoServerService {
 		private userEntityService: UserEntityService,
 		private metaService: MetaService,
 	) {
+		this.createServer = this.createServer.bind(this);
 	}
 
 	public getLinks() {
@@ -39,9 +40,7 @@ export class NodeinfoServerService {
 			}];
 	}
 
-	public createRouter() {
-		const router = new Router();
-
+	public createServer(fastify: FastifyInstance, options: FastifyPluginOptions, done: (err?: Error) => void) {
 		const nodeinfo2 = async () => {
 			const now = Date.now();
 			const [
@@ -108,22 +107,22 @@ export class NodeinfoServerService {
 
 		const cache = new Cache<Awaited<ReturnType<typeof nodeinfo2>>>(1000 * 60 * 10);
 
-		router.get(nodeinfo2_1path, async ctx => {
+		fastify.get(nodeinfo2_1path, async (request, reply) => {
 			const base = await cache.fetch(null, () => nodeinfo2());
 
-			ctx.body = { version: '2.1', ...base };
-			ctx.set('Cache-Control', 'public, max-age=600');
+			reply.header('Cache-Control', 'public, max-age=600');
+			return { version: '2.1', ...base };
 		});
 
-		router.get(nodeinfo2_0path, async ctx => {
+		fastify.get(nodeinfo2_0path, async (request, reply) => {
 			const base = await cache.fetch(null, () => nodeinfo2());
 
 			delete (base as any).software.repository;
 
-			ctx.body = { version: '2.0', ...base };
-			ctx.set('Cache-Control', 'public, max-age=600');
+			reply.header('Cache-Control', 'public, max-age=600');
+			return { version: '2.0', ...base };
 		});
 
-		return router;
+		done();
 	}
 }
diff --git a/packages/backend/src/server/ServerService.ts b/packages/backend/src/server/ServerService.ts
index d42972614f..96159cfc53 100644
--- a/packages/backend/src/server/ServerService.ts
+++ b/packages/backend/src/server/ServerService.ts
@@ -2,11 +2,7 @@ import cluster from 'node:cluster';
 import * as fs from 'node:fs';
 import * as http from 'node:http';
 import { Inject, Injectable } from '@nestjs/common';
-import Koa from 'koa';
-import Router from '@koa/router';
-import mount from 'koa-mount';
-import koaLogger from 'koa-logger';
-import * as slow from 'koa-slow';
+import Fastify from 'fastify';
 import { IsNull } from 'typeorm';
 import { GlobalEventService } from '@/core/GlobalEventService.js';
 import type { Config } from '@/config.js';
@@ -58,47 +54,29 @@ export class ServerService {
 	}
 
 	public launch() {
-		// Init app
-		const koa = new Koa();
-		koa.proxy = true;
-
-		if (!['production', 'test'].includes(process.env.NODE_ENV ?? '')) {
-		// Logger
-			koa.use(koaLogger(str => {
-				this.logger.info(str);
-			}));
-
-			// Delay
-			if (envOption.slow) {
-				koa.use(slow({
-					delay: 3000,
-				}));
-			}
-		}
+		const fastify = Fastify({
+			trustProxy: true,
+			logger: !['production', 'test'].includes(process.env.NODE_ENV ?? ''),
+		});
 
 		// HSTS
 		// 6months (15552000sec)
 		if (this.config.url.startsWith('https') && !this.config.disableHsts) {
-			koa.use(async (ctx, next) => {
-				ctx.set('strict-transport-security', 'max-age=15552000; preload');
-				await next();
+			fastify.addHook('onRequest', (request, reply, done) => {
+				reply.header('strict-transport-security', 'max-age=15552000; preload');
+				done();
 			});
 		}
 
-		koa.use(mount('/api', this.apiServerService.createApiServer(koa)));
-		koa.use(mount('/files', this.fileServerService.createServer()));
-		koa.use(mount('/proxy', this.mediaProxyServerService.createServer()));
+		fastify.register(this.apiServerService.createServer, { prefix: '/api' });
+		fastify.register(this.fileServerService.createServer, { prefix: '/files' });
+		fastify.register(this.mediaProxyServerService.createServer, { prefix: '/proxy' });
+		fastify.register(this.activityPubServerService.createServer);
+		fastify.register(this.nodeinfoServerService.createServer);
+		fastify.register(this.wellKnownServerService.createServer);
 
-		// Init router
-		const router = new Router();
-
-		// Routing
-		router.use(this.activityPubServerService.createRouter().routes());
-		router.use(this.nodeinfoServerService.createRouter().routes());
-		router.use(this.wellKnownServerService.createRouter().routes());
-
-		router.get('/avatar/@:acct', async ctx => {
-			const { username, host } = Acct.parse(ctx.params.acct);
+		fastify.get<{ Params: { acct: string } }>('/avatar/@:acct', async (request, reply) => {
+			const { username, host } = Acct.parse(request.params.acct);
 			const user = await this.usersRepository.findOne({
 				where: {
 					usernameLower: username.toLowerCase(),
@@ -109,28 +87,25 @@ export class ServerService {
 			});
 
 			if (user) {
-				ctx.redirect(this.userEntityService.getAvatarUrlSync(user));
+				reply.redirect(this.userEntityService.getAvatarUrlSync(user));
 			} else {
-				ctx.redirect('/static-assets/user-unknown.png');
+				reply.redirect('/static-assets/user-unknown.png');
 			}
 		});
 
-		router.get('/identicon/:x', async ctx => {
+		fastify.get<{ Params: { x: string } }>('/identicon/:x', async (request, reply) => {
 			const [temp, cleanup] = await createTemp();
-			await genIdenticon(ctx.params.x, fs.createWriteStream(temp));
-			ctx.set('Content-Type', 'image/png');
-			ctx.body = fs.createReadStream(temp).on('close', () => cleanup());
+			await genIdenticon(request.params.x, fs.createWriteStream(temp));
+			reply.header('Content-Type', 'image/png');
+			return fs.createReadStream(temp).on('close', () => cleanup());
 		});
 
-		router.get('/verify-email/:code', async ctx => {
+		fastify.get<{ Params: { code: string } }>('/verify-email/:code', async (request, reply) => {
 			const profile = await this.userProfilesRepository.findOneBy({
-				emailVerifyCode: ctx.params.code,
+				emailVerifyCode: request.params.code,
 			});
 
 			if (profile != null) {
-				ctx.body = 'Verify succeeded!';
-				ctx.status = 200;
-
 				await this.userProfilesRepository.update({ userId: profile.userId }, {
 					emailVerified: true,
 					emailVerifyCode: null,
@@ -140,21 +115,19 @@ export class ServerService {
 					detail: true,
 					includeSecrets: true,
 				}));
+
+				reply.code(200);
+				return 'Verify succeeded!';
 			} else {
-				ctx.status = 404;
+				reply.code(404);
 			}
 		});
 
-		// Register router
-		koa.use(router.routes());
-
-		koa.use(mount(this.clientServerService.createApp()));
-
-		const server = http.createServer(koa.callback());
+		fastify.register(this.clientServerService.createServer);
 
-		this.streamingApiServerService.attachStreamingApi(server);
+		this.streamingApiServerService.attachStreamingApi(fastify.server);
 
-		server.on('error', err => {
+		fastify.server.on('error', err => {
 			switch ((err as any).code) {
 				case 'EACCES':
 					this.logger.error(`You do not have permission to listen on port ${this.config.port}.`);
@@ -168,13 +141,13 @@ export class ServerService {
 			}
 
 			if (cluster.isWorker) {
-			process.send!('listenFailed');
+				process.send!('listenFailed');
 			} else {
-			// disableClustering
+				// disableClustering
 				process.exit(1);
 			}
 		});
 
-		server.listen(this.config.port);
+		fastify.listen({ port: this.config.port });
 	}
 }
diff --git a/packages/backend/src/server/WellKnownServerService.ts b/packages/backend/src/server/WellKnownServerService.ts
index f2eee88e09..412c608313 100644
--- a/packages/backend/src/server/WellKnownServerService.ts
+++ b/packages/backend/src/server/WellKnownServerService.ts
@@ -1,6 +1,7 @@
 import { Inject, Injectable } from '@nestjs/common';
-import Router from '@koa/router';
+import { FastifyInstance, FastifyPluginOptions, FastifyReply, FastifyRequest } from 'fastify';
 import { IsNull, MoreThan } from 'typeorm';
+import vary from 'vary';
 import { DI } from '@/di-symbols.js';
 import type { UsersRepository } from '@/models/index.js';
 import type { Config } from '@/config.js';
@@ -21,11 +22,10 @@ export class WellKnownServerService {
 
 		private nodeinfoServerService: NodeinfoServerService,
 	) {
+		this.createServer = this.createServer.bind(this);
 	}
 
-	public createRouter() {
-		const router = new Router();
-
+	public createServer(fastify: FastifyInstance, options: FastifyPluginOptions, done: (err?: Error) => void) {
 		const XRD = (...x: { element: string, value?: string, attributes?: Record<string, string> }[]) =>
 			`<?xml version="1.0" encoding="UTF-8"?><XRD xmlns="http://docs.oasis-open.org/ns/xri/xrd-1.0">${x.map(({ element, value, attributes }) =>
 				`<${
@@ -34,37 +34,35 @@ export class WellKnownServerService {
 					typeof value === 'string' ? `>${escapeValue(value)}</${element}` : '/'
 				}>`).reduce((a, c) => a + c, '')}</XRD>`;
 
-		const allPath = '/.well-known/(.*)';
+		const allPath = '/.well-known/*';
 		const webFingerPath = '/.well-known/webfinger';
 		const jrd = 'application/jrd+json';
 		const xrd = 'application/xrd+xml';
 
-		router.use(allPath, async (ctx, next) => {
-			ctx.set({
-				'Access-Control-Allow-Headers': 'Accept',
-				'Access-Control-Allow-Methods': 'GET, OPTIONS',
-				'Access-Control-Allow-Origin': '*',
-				'Access-Control-Expose-Headers': 'Vary',
-			});
-			await next();
+		fastify.addHook('onRequest', (request, reply, done) => {
+			reply.header('Access-Control-Allow-Headers', 'Accept');
+			reply.header('Access-Control-Allow-Methods', 'GET, OPTIONS');
+			reply.header('Access-Control-Allow-Origin', '*');
+			reply.header('Access-Control-Expose-Headers', 'Vary');
+			done();
 		});
 
-		router.options(allPath, async ctx => {
-			ctx.status = 204;
+		fastify.options(allPath, async (request, reply) => {
+			reply.code(204);
 		});
 
-		router.get('/.well-known/host-meta', async ctx => {
-			ctx.set('Content-Type', xrd);
-			ctx.body = XRD({ element: 'Link', attributes: {
+		fastify.get('/.well-known/host-meta', async (request, reply) => {
+			reply.header('Content-Type', xrd);
+			return XRD({ element: 'Link', attributes: {
 				rel: 'lrdd',
 				type: xrd,
 				template: `${this.config.url}${webFingerPath}?resource={uri}`,
 			} });
 		});
 
-		router.get('/.well-known/host-meta.json', async ctx => {
-			ctx.set('Content-Type', jrd);
-			ctx.body = {
+		fastify.get('/.well-known/host-meta.json', async (request, reply) => {
+			reply.header('Content-Type', jrd);
+			return {
 				links: [{
 					rel: 'lrdd',
 					type: jrd,
@@ -73,16 +71,16 @@ export class WellKnownServerService {
 			};
 		});
 
-		router.get('/.well-known/nodeinfo', async ctx => {
-			ctx.body = { links: this.nodeinfoServerService.getLinks() };
+		fastify.get('/.well-known/nodeinfo', async (request, reply) => {
+			return { links: this.nodeinfoServerService.getLinks() };
 		});
 
 		/* TODO
-router.get('/.well-known/change-password', async ctx => {
+fastify.get('/.well-known/change-password', async (request, reply) => {
 });
 */
 
-		router.get(webFingerPath, async ctx => {
+		fastify.get<{ Querystring: { resource: string } }>(webFingerPath, async (request, reply) => {
 			const fromId = (id: User['id']): FindOptionsWhere<User> => ({
 				id,
 				host: IsNull(),
@@ -104,22 +102,22 @@ router.get('/.well-known/change-password', async ctx => {
 					isSuspended: false,
 				} : 422;
 
-			if (typeof ctx.query.resource !== 'string') {
-				ctx.status = 400;
+			if (typeof request.query.resource !== 'string') {
+				reply.code(400);
 				return;
 			}
 
-			const query = generateQuery(ctx.query.resource.toLowerCase());
+			const query = generateQuery(request.query.resource.toLowerCase());
 
 			if (typeof query === 'number') {
-				ctx.status = query;
+				reply.code(query);
 				return;
 			}
 
 			const user = await this.usersRepository.findOneBy(query);
 
 			if (user == null) {
-				ctx.status = 404;
+				reply.code(404);
 				return;
 			}
 
@@ -139,30 +137,25 @@ router.get('/.well-known/change-password', async ctx => {
 				template: `${this.config.url}/authorize-follow?acct={uri}`,
 			};
 
-			if (ctx.accepts(jrd, xrd) === xrd) {
-				ctx.body = XRD(
+			vary(reply.raw, 'Accept');
+			reply.header('Cache-Control', 'public, max-age=180');
+
+			if (request.accepts().type([jrd, xrd]) === xrd) {
+				reply.type(xrd);
+				return XRD(
 					{ element: 'Subject', value: subject },
 					{ element: 'Link', attributes: self },
 					{ element: 'Link', attributes: profilePage },
 					{ element: 'Link', attributes: subscribe });
-				ctx.type = xrd;
 			} else {
-				ctx.body = {
+				reply.type(jrd);
+				return {
 					subject,
 					links: [self, profilePage, subscribe],
 				};
-				ctx.type = jrd;
 			}
-
-			ctx.vary('Accept');
-			ctx.set('Cache-Control', 'public, max-age=180');
-		});
-
-		// Return 404 for other .well-known
-		router.all(allPath, async ctx => {
-			ctx.status = 404;
 		});
 
-		return router;
+		done();
 	}
 }
diff --git a/packages/backend/src/server/api/ApiCallService.ts b/packages/backend/src/server/api/ApiCallService.ts
index c3ce12e0c3..2e72cdf9f8 100644
--- a/packages/backend/src/server/api/ApiCallService.ts
+++ b/packages/backend/src/server/api/ApiCallService.ts
@@ -1,19 +1,25 @@
 import { performance } from 'perf_hooks';
+import { pipeline } from 'node:stream';
+import * as fs from 'node:fs';
+import { promisify } from 'node:util';
 import { Inject, Injectable } from '@nestjs/common';
+import { FastifyRequest, FastifyReply } from 'fastify';
 import { DI } from '@/di-symbols.js';
 import { getIpHash } from '@/misc/get-ip-hash.js';
-import type { CacheableLocalUser, User } from '@/models/entities/User.js';
+import type { CacheableLocalUser, ILocalUser, User } from '@/models/entities/User.js';
 import type { AccessToken } from '@/models/entities/AccessToken.js';
 import type Logger from '@/logger.js';
 import type { UserIpsRepository } from '@/models/index.js';
 import { MetaService } from '@/core/MetaService.js';
+import { createTemp } from '@/misc/create-temp.js';
 import { ApiError } from './error.js';
 import { RateLimiterService } from './RateLimiterService.js';
 import { ApiLoggerService } from './ApiLoggerService.js';
 import { AuthenticateService, AuthenticationError } from './AuthenticateService.js';
 import type { OnApplicationShutdown } from '@nestjs/common';
 import type { IEndpointMeta, IEndpoint } from './endpoints.js';
-import type Koa from 'koa';
+
+const pump = promisify(pipeline);
 
 const accessDenied = {
 	message: 'Access denied.',
@@ -44,92 +50,149 @@ export class ApiCallService implements OnApplicationShutdown {
 		}, 1000 * 60 * 60);
 	}
 
-	public handleRequest(endpoint: IEndpoint, exec: any, ctx: Koa.Context) {
-		return new Promise<void>((res) => {
-			const body = ctx.is('multipart/form-data')
-				? (ctx.request as any).body
-				: ctx.method === 'GET'
-					? ctx.query
-					: ctx.request.body;
-		
-			const reply = (x?: any, y?: ApiError) => {
-				if (x == null) {
-					ctx.status = 204;
-				} else if (typeof x === 'number' && y) {
-					ctx.status = x;
-					ctx.body = {
-						error: {
-							message: y!.message,
-							code: y!.code,
-							id: y!.id,
-							kind: y!.kind,
-							...(y!.info ? { info: y!.info } : {}),
-						},
-					};
-				} else {
-					// 文字列を返す場合は、JSON.stringify通さないとJSONと認識されない
-					ctx.body = typeof x === 'string' ? JSON.stringify(x) : x;
-				}
-				res();
-			};
-		
-			// Authentication
-			this.authenticateService.authenticate(body['i']).then(([user, app]) => {
-				// API invoking
-				this.call(endpoint, exec, user, app, body, ctx).then((res: any) => {
-					if (ctx.method === 'GET' && endpoint.meta.cacheSec && !body['i'] && !user) {
-						ctx.set('Cache-Control', `public, max-age=${endpoint.meta.cacheSec}`);
-					}
-					reply(res);
-				}).catch((e: ApiError) => {
-					reply(e.httpStatusCode ? e.httpStatusCode : e.kind === 'client' ? 400 : 500, e);
-				});
-		
-				// Log IP
-				if (user) {
-					this.metaService.fetch().then(meta => {
-						if (!meta.enableIpLogging) return;
-						const ip = ctx.ip;
-						const ips = this.userIpHistories.get(user.id);
-						if (ips == null || !ips.has(ip)) {
-							if (ips == null) {
-								this.userIpHistories.set(user.id, new Set([ip]));
-							} else {
-								ips.add(ip);
-							}
-		
-							try {
-								this.userIpsRepository.createQueryBuilder().insert().values({
-									createdAt: new Date(),
-									userId: user.id,
-									ip: ip,
-								}).orIgnore(true).execute();
-							} catch {
-							}
-						}
-					});
-				}
-			}).catch(e => {
-				if (e instanceof AuthenticationError) {
-					reply(403, new ApiError({
-						message: 'Authentication failed. Please ensure your token is correct.',
-						code: 'AUTHENTICATION_FAILED',
-						id: 'b0a7f5f8-dc2f-4171-b91f-de88ad238e14',
-					}));
-				} else {
-					reply(500, new ApiError());
+	public handleRequest(
+		endpoint: IEndpoint & { exec: any },
+		request: FastifyRequest<{ Body: Record<string, unknown>, Querystring: Record<string, unknown> }>,
+		reply: FastifyReply,
+	) {
+		const body = request.method === 'GET'
+			? request.query
+			: request.body;
+
+		const token = body['i'];
+		if (token != null && typeof token !== 'string') {
+			reply.code(400);
+			return;
+		}
+		this.authenticateService.authenticate(token).then(([user, app]) => {
+			this.call(endpoint, user, app, body, null, request).then((res) => {
+				if (request.method === 'GET' && endpoint.meta.cacheSec && !body['i'] && !user) {
+					reply.header('Cache-Control', `public, max-age=${endpoint.meta.cacheSec}`);
 				}
+				this.send(reply, res);
+			}).catch((err: ApiError) => {
+				this.send(reply, err.httpStatusCode ? err.httpStatusCode : err.kind === 'client' ? 400 : 500, err);
 			});
+
+			if (user) {
+				this.logIp(request, user);
+			}
+		}).catch(err => {
+			if (err instanceof AuthenticationError) {
+				this.send(reply, 403, new ApiError({
+					message: 'Authentication failed. Please ensure your token is correct.',
+					code: 'AUTHENTICATION_FAILED',
+					id: 'b0a7f5f8-dc2f-4171-b91f-de88ad238e14',
+				}));
+			} else {
+				this.send(reply, 500, new ApiError());
+			}
 		});
 	}
 
+	public async handleMultipartRequest(
+		endpoint: IEndpoint & { exec: any },
+		request: FastifyRequest<{ Body: Record<string, unknown>, Querystring: Record<string, unknown> }>,
+		reply: FastifyReply,
+	) {
+		const multipartData = await request.file();
+		if (multipartData == null) {
+			reply.code(400);
+			return;
+		}
+
+		const [path] = await createTemp();
+		await pump(multipartData.file, fs.createWriteStream(path));
+
+		const fields = {} as Record<string, string | undefined>;
+		for (const [k, v] of Object.entries(multipartData.fields)) {
+			fields[k] = v.value;
+		}
+	
+		const token = fields['i'];
+		if (token != null && typeof token !== 'string') {
+			reply.code(400);
+			return;
+		}
+		this.authenticateService.authenticate(token).then(([user, app]) => {
+			this.call(endpoint, user, app, fields, {
+				name: multipartData.filename,
+				path: path,
+			}, request).then((res) => {
+				this.send(reply, res);
+			}).catch((err: ApiError) => {
+				this.send(reply, err.httpStatusCode ? err.httpStatusCode : err.kind === 'client' ? 400 : 500, err);
+			});
+
+			if (user) {
+				this.logIp(request, user);
+			}
+		}).catch(err => {
+			if (err instanceof AuthenticationError) {
+				this.send(reply, 403, new ApiError({
+					message: 'Authentication failed. Please ensure your token is correct.',
+					code: 'AUTHENTICATION_FAILED',
+					id: 'b0a7f5f8-dc2f-4171-b91f-de88ad238e14',
+				}));
+			} else {
+				this.send(reply, 500, new ApiError());
+			}
+		});
+	}
+
+	private send(reply: FastifyReply, x?: any, y?: ApiError) {
+		if (x == null) {
+			reply.code(204);
+		} else if (typeof x === 'number' && y) {
+			reply.code(x);
+			reply.send({
+				error: {
+					message: y!.message,
+					code: y!.code,
+					id: y!.id,
+					kind: y!.kind,
+					...(y!.info ? { info: y!.info } : {}),
+				},
+			});
+		} else {
+			// 文字列を返す場合は、JSON.stringify通さないとJSONと認識されない
+			reply.send(typeof x === 'string' ? JSON.stringify(x) : x);
+		}
+	}
+
+	private async logIp(request: FastifyRequest, user: ILocalUser) {
+		const meta = await this.metaService.fetch();
+		if (!meta.enableIpLogging) return;
+		const ip = request.ip;
+		const ips = this.userIpHistories.get(user.id);
+		if (ips == null || !ips.has(ip)) {
+			if (ips == null) {
+				this.userIpHistories.set(user.id, new Set([ip]));
+			} else {
+				ips.add(ip);
+			}
+
+			try {
+				this.userIpsRepository.createQueryBuilder().insert().values({
+					createdAt: new Date(),
+					userId: user.id,
+					ip: ip,
+				}).orIgnore(true).execute();
+			} catch {
+			}
+		}
+	}
+
 	private async call(
-		ep: IEndpoint,
-		exec: any,
+		ep: IEndpoint & { exec: any },
 		user: CacheableLocalUser | null | undefined,
 		token: AccessToken | null | undefined,
 		data: any,
-		ctx?: Koa.Context,
+		file: {
+			name: string;
+			path: string;
+		} | null,
+		request: FastifyRequest<{ Body: Record<string, unknown>, Querystring: Record<string, unknown> }>,
 	) {
 		const isSecure = user != null && token == null;
 		const isModerator = user != null && (user.isModerator || user.isAdmin);
@@ -144,7 +207,7 @@ export class ApiCallService implements OnApplicationShutdown {
 			if (user) {
 				limitActor = user.id;
 			} else {
-				limitActor = getIpHash(ctx!.ip);
+				limitActor = getIpHash(request.ip);
 			}
 
 			const limit = Object.assign({}, ep.meta.limit);
@@ -154,7 +217,7 @@ export class ApiCallService implements OnApplicationShutdown {
 			}
 
 			// Rate limit
-			await this.rateLimiterService.limit(limit as IEndpointMeta['limit'] & { key: NonNullable<string> }, limitActor).catch(e => {
+			await this.rateLimiterService.limit(limit as IEndpointMeta['limit'] & { key: NonNullable<string> }, limitActor).catch(err => {
 				throw new ApiError({
 					message: 'Rate limit exceeded. Please try again later.',
 					code: 'RATE_LIMIT_EXCEEDED',
@@ -199,7 +262,7 @@ export class ApiCallService implements OnApplicationShutdown {
 		}
 
 		// Cast non JSON input
-		if ((ep.meta.requireFile || ctx?.method === 'GET') && ep.params.properties) {
+		if ((ep.meta.requireFile || request.method === 'GET') && ep.params.properties) {
 			for (const k of Object.keys(ep.params.properties)) {
 				const param = ep.params.properties![k];
 				if (['boolean', 'number', 'integer'].includes(param.type ?? '') && typeof data[k] === 'string') {
@@ -221,7 +284,7 @@ export class ApiCallService implements OnApplicationShutdown {
 
 		// API invoking
 		const before = performance.now();
-		return await exec(data, user, token, ctx?.file, ctx?.ip, ctx?.headers).catch((err: Error) => {
+		return await ep.exec(data, user, token, file, request.ip, request.headers).catch((err: Error) => {
 			if (err instanceof ApiError) {
 				throw err;
 			} else {
diff --git a/packages/backend/src/server/api/ApiServerService.ts b/packages/backend/src/server/api/ApiServerService.ts
index 52654dbaee..cf3f2deebf 100644
--- a/packages/backend/src/server/api/ApiServerService.ts
+++ b/packages/backend/src/server/api/ApiServerService.ts
@@ -1,15 +1,13 @@
 import { Inject, Injectable } from '@nestjs/common';
-import Koa from 'koa';
-import Router from '@koa/router';
-import multer from '@koa/multer';
-import bodyParser from 'koa-bodyparser';
-import cors from '@koa/cors';
-import { ModuleRef } from '@nestjs/core';
+import { FastifyInstance, FastifyPluginOptions } from 'fastify';
+import cors from '@fastify/cors';
+import multipart from '@fastify/multipart';
+import { ModuleRef, repl } from '@nestjs/core';
 import type { Config } from '@/config.js';
 import type { UsersRepository, InstancesRepository, AccessTokensRepository } from '@/models/index.js';
 import { DI } from '@/di-symbols.js';
 import { UserEntityService } from '@/core/entities/UserEntityService.js';
-import endpoints from './endpoints.js';
+import endpoints, { IEndpoint } from './endpoints.js';
 import { ApiCallService } from './ApiCallService.js';
 import { SignupApiService } from './SignupApiService.js';
 import { SigninApiService } from './SigninApiService.js';
@@ -42,92 +40,107 @@ export class ApiServerService {
 		private discordServerService: DiscordServerService,
 		private twitterServerService: TwitterServerService,
 	) {
+		this.createServer = this.createServer.bind(this);
 	}
 
-	public createApiServer() {
-		const handlers: Record<string, any> = {};
-
-		for (const endpoint of endpoints) {
-			handlers[endpoint.name] = this.moduleRef.get('ep:' + endpoint.name, { strict: false }).exec;
-		}
-
-		// Init app
-		const apiServer = new Koa();
-
-		apiServer.use(cors({
+	public createServer(fastify: FastifyInstance, options: FastifyPluginOptions, done: (err?: Error) => void) {
+		fastify.register(cors, {
 			origin: '*',
-		}));
-
-		// No caching
-		apiServer.use(async (ctx, next) => {
-			ctx.set('Cache-Control', 'private, max-age=0, must-revalidate');
-			await next();
 		});
 
-		apiServer.use(bodyParser({
-			// リクエストが multipart/form-data でない限りはJSONだと見なす
-			detectJSON: ctx => !ctx.is('multipart/form-data'),
-		}));
-
-		// Init multer instance
-		const upload = multer({
-			storage: multer.diskStorage({}),
+		fastify.register(multipart, {
 			limits: {
 				fileSize: this.config.maxFileSize ?? 262144000,
 				files: 1,
 			},
 		});
 
-		// Init router
-		const router = new Router();
+		// Prevent cache
+		fastify.addHook('onRequest', (request, reply, done) => {
+			reply.header('Cache-Control', 'private, max-age=0, must-revalidate');
+			done();
+		});
 
-		/**
-		 * Register endpoint handlers
-		 */
 		for (const endpoint of endpoints) {
+			const ep = {
+				name: endpoint.name,
+				meta: endpoint.meta,
+				params: endpoint.params,
+				exec: this.moduleRef.get('ep:' + endpoint.name, { strict: false }).exec,
+			};
+
 			if (endpoint.meta.requireFile) {
-				router.post(`/${endpoint.name}`, upload.single('file'), this.apiCallService.handleRequest.bind(this.apiCallService, endpoint, handlers[endpoint.name]));
+				fastify.all<{
+					Params: { endpoint: string; },
+					Body: Record<string, unknown>,
+					Querystring: Record<string, unknown>,
+				}>('/' + endpoint.name, (request, reply) => {
+					if (request.method === 'GET' && !endpoint.meta.allowGet) {
+						reply.code(405);
+						return;
+					}
+		
+					this.apiCallService.handleMultipartRequest(ep, request, reply);
+				});
 			} else {
-				// 後方互換性のため
-				if (endpoint.name.includes('-')) {
-					router.post(`/${endpoint.name.replace(/-/g, '_')}`, this.apiCallService.handleRequest.bind(this.apiCallService, endpoint, handlers[endpoint.name]));
-
-					if (endpoint.meta.allowGet) {
-						router.get(`/${endpoint.name.replace(/-/g, '_')}`, this.apiCallService.handleRequest.bind(this.apiCallService, endpoint, handlers[endpoint.name]));
-					} else {
-						router.get(`/${endpoint.name.replace(/-/g, '_')}`, async ctx => { ctx.status = 405; });
+				fastify.all<{
+					Params: { endpoint: string; },
+					Body: Record<string, unknown>,
+					Querystring: Record<string, unknown>,
+				}>('/' + endpoint.name, (request, reply) => {
+					if (request.method === 'GET' && !endpoint.meta.allowGet) {
+						reply.code(405);
+						return;
 					}
-				}
-
-				router.post(`/${endpoint.name}`, this.apiCallService.handleRequest.bind(this.apiCallService, endpoint, handlers[endpoint.name]));
-
-				if (endpoint.meta.allowGet) {
-					router.get(`/${endpoint.name}`, this.apiCallService.handleRequest.bind(this.apiCallService, endpoint, handlers[endpoint.name]));
-				} else {
-					router.get(`/${endpoint.name}`, async ctx => { ctx.status = 405; });
-				}
+		
+					this.apiCallService.handleRequest(ep, request, reply);
+				});
 			}
 		}
 
-		router.post('/signup', ctx => this.signupApiServiceService.signup(ctx));
-		router.post('/signin', ctx => this.signinApiServiceService.signin(ctx));
-		router.post('/signup-pending', ctx => this.signupApiServiceService.signupPending(ctx));
+		fastify.post<{
+			Body: {
+				username: string;
+				password: string;
+				host?: string;
+				invitationCode?: string;
+				emailAddress?: string;
+				'hcaptcha-response'?: string;
+				'g-recaptcha-response'?: string;
+				'turnstile-response'?: string;
+			}
+		}>('/signup', (request, reply) => this.signupApiServiceService.signup(request, reply));
+
+		fastify.post<{
+			Body: {
+				username: string;
+				password: string;
+				token?: string;
+				signature?: string;
+				authenticatorData?: string;
+				clientDataJSON?: string;
+				credentialId?: string;
+				challengeId?: string;
+			};
+		}>('/signin', (request, reply) => this.signinApiServiceService.signin(request, reply));
+
+		fastify.post<{ Body: { code: string; } }>('/signup-pending', (request, reply) => this.signupApiServiceService.signupPending(request, reply));
 
-		router.use(this.discordServerService.create().routes());
-		router.use(this.githubServerService.create().routes());
-		router.use(this.twitterServerService.create().routes());
+		fastify.register(this.discordServerService.create);
+		fastify.register(this.githubServerService.create);
+		fastify.register(this.twitterServerService.create);
 
-		router.get('/v1/instance/peers', async ctx => {
+		fastify.get('/v1/instance/peers', async (request, reply) => {
 			const instances = await this.instancesRepository.find({
 				select: ['host'],
 			});
 
-			ctx.body = instances.map(instance => instance.host);
+			return instances.map(instance => instance.host);
 		});
 
-		router.post('/miauth/:session/check', async ctx => {
+		fastify.post<{ Params: { session: string; } }>('/miauth/:session/check', async (request, reply) => {
 			const token = await this.accessTokensRepository.findOneBy({
-				session: ctx.params.session,
+				session: request.params.session,
 			});
 
 			if (token && token.session != null && !token.fetched) {
@@ -135,26 +148,18 @@ export class ApiServerService {
 					fetched: true,
 				});
 
-				ctx.body = {
+				return {
 					ok: true,
 					token: token.token,
 					user: await this.userEntityService.pack(token.userId, null, { detail: true }),
 				};
 			} else {
-				ctx.body = {
+				return {
 					ok: false,
 				};
 			}
 		});
 
-		// Return 404 for unknown API
-		router.all('(.*)', async ctx => {
-			ctx.status = 404;
-		});
-
-		// Register router
-		apiServer.use(router.routes());
-
-		return apiServer;
+		done();
 	}
 }
diff --git a/packages/backend/src/server/api/AuthenticateService.ts b/packages/backend/src/server/api/AuthenticateService.ts
index 4ce9b91f42..ad387c4732 100644
--- a/packages/backend/src/server/api/AuthenticateService.ts
+++ b/packages/backend/src/server/api/AuthenticateService.ts
@@ -34,7 +34,7 @@ export class AuthenticateService {
 		this.appCache = new Cache<App>(Infinity);
 	}
 
-	public async authenticate(token: string | null): Promise<[CacheableLocalUser | null | undefined, AccessToken | null | undefined]> {
+	public async authenticate(token: string | null | undefined): Promise<[CacheableLocalUser | null | undefined, AccessToken | null | undefined]> {
 		if (token == null) {
 			return [null, null];
 		}
diff --git a/packages/backend/src/server/api/SigninApiService.ts b/packages/backend/src/server/api/SigninApiService.ts
index a5e2b09012..8b3d86e5a6 100644
--- a/packages/backend/src/server/api/SigninApiService.ts
+++ b/packages/backend/src/server/api/SigninApiService.ts
@@ -3,6 +3,7 @@ import { Inject, Injectable } from '@nestjs/common';
 import bcrypt from 'bcryptjs';
 import * as speakeasy from 'speakeasy';
 import { IsNull } from 'typeorm';
+import { FastifyInstance, FastifyRequest, FastifyReply } from 'fastify';
 import { DI } from '@/di-symbols.js';
 import type { UserSecurityKeysRepository, SigninsRepository, UserProfilesRepository, AttestationChallengesRepository, UsersRepository } from '@/models/index.js';
 import type { Config } from '@/config.js';
@@ -12,7 +13,6 @@ import { IdService } from '@/core/IdService.js';
 import { TwoFactorAuthenticationService } from '@/core/TwoFactorAuthenticationService.js';
 import { RateLimiterService } from './RateLimiterService.js';
 import { SigninService } from './SigninService.js';
-import type Koa from 'koa';
 
 @Injectable()
 export class SigninApiService {
@@ -42,47 +42,60 @@ export class SigninApiService {
 	) {
 	}
 
-	public async signin(ctx: Koa.Context) {
-		ctx.set('Access-Control-Allow-Origin', this.config.url);
-		ctx.set('Access-Control-Allow-Credentials', 'true');
+	public async signin(
+		request: FastifyRequest<{
+			Body: {
+				username: string;
+				password: string;
+				token?: string;
+				signature?: string;
+				authenticatorData?: string;
+				clientDataJSON?: string;
+				credentialId?: string;
+				challengeId?: string;
+			};
+		}>,
+		reply: FastifyReply,
+	) {
+		reply.header('Access-Control-Allow-Origin', this.config.url);
+		reply.header('Access-Control-Allow-Credentials', 'true');
 
-		const body = ctx.request.body as any;
+		const body = request.body;
 		const username = body['username'];
 		const password = body['password'];
 		const token = body['token'];
 
 		function error(status: number, error: { id: string }) {
-			ctx.status = status;
-			ctx.body = { error };
+			reply.code(status);
+			return { error };
 		}
 
 		try {
 		// not more than 1 attempt per second and not more than 10 attempts per hour
-			await this.rateLimiterService.limit({ key: 'signin', duration: 60 * 60 * 1000, max: 10, minInterval: 1000 }, getIpHash(ctx.ip));
+			await this.rateLimiterService.limit({ key: 'signin', duration: 60 * 60 * 1000, max: 10, minInterval: 1000 }, getIpHash(request.ip));
 		} catch (err) {
-			ctx.status = 429;
-			ctx.body = {
+			reply.code(429);
+			return {
 				error: {
 					message: 'Too many failed attempts to sign in. Try again later.',
 					code: 'TOO_MANY_AUTHENTICATION_FAILURES',
 					id: '22d05606-fbcf-421a-a2db-b32610dcfd1b',
 				},
 			};
-			return;
 		}
 
 		if (typeof username !== 'string') {
-			ctx.status = 400;
+			reply.code(400);
 			return;
 		}
 
 		if (typeof password !== 'string') {
-			ctx.status = 400;
+			reply.code(400);
 			return;
 		}
 
 		if (token != null && typeof token !== 'string') {
-			ctx.status = 400;
+			reply.code(400);
 			return;
 		}
 
@@ -93,17 +106,15 @@ export class SigninApiService {
 		}) as ILocalUser;
 
 		if (user == null) {
-			error(404, {
+			return error(404, {
 				id: '6cc579cc-885d-43d8-95c2-b8c7fc963280',
 			});
-			return;
 		}
 
 		if (user.isSuspended) {
-			error(403, {
+			return error(403, {
 				id: 'e03a5f46-d309-4865-9b69-56282d94e1eb',
 			});
-			return;
 		}
 
 		const profile = await this.userProfilesRepository.findOneByOrFail({ userId: user.id });
@@ -117,32 +128,29 @@ export class SigninApiService {
 				id: this.idService.genId(),
 				createdAt: new Date(),
 				userId: user.id,
-				ip: ctx.ip,
-				headers: ctx.headers,
+				ip: request.ip,
+				headers: request.headers,
 				success: false,
 			});
 
-			error(status ?? 500, failure ?? { id: '4e30e80c-e338-45a0-8c8f-44455efa3b76' });
+			return error(status ?? 500, failure ?? { id: '4e30e80c-e338-45a0-8c8f-44455efa3b76' });
 		};
 
 		if (!profile.twoFactorEnabled) {
 			if (same) {
-				this.signinService.signin(ctx, user);
-				return;
+				return this.signinService.signin(request, reply, user);
 			} else {
-				await fail(403, {
+				return await fail(403, {
 					id: '932c904e-9460-45b7-9ce6-7ed33be7eb2c',
 				});
-				return;
 			}
 		}
 
 		if (token) {
 			if (!same) {
-				await fail(403, {
+				return await fail(403, {
 					id: '932c904e-9460-45b7-9ce6-7ed33be7eb2c',
 				});
-				return;
 			}
 
 			const verified = (speakeasy as any).totp.verify({
@@ -153,20 +161,17 @@ export class SigninApiService {
 			});
 
 			if (verified) {
-				this.signinService.signin(ctx, user);
-				return;
+				return this.signinService.signin(request, reply, user);
 			} else {
-				await fail(403, {
+				return await fail(403, {
 					id: 'cdf1235b-ac71-46d4-a3a6-84ccce48df6f',
 				});
-				return;
 			}
-		} else if (body.credentialId) {
+		} else if (body.credentialId && body.clientDataJSON && body.authenticatorData && body.signature) {
 			if (!same && !profile.usePasswordLessLogin) {
-				await fail(403, {
+				return await fail(403, {
 					id: '932c904e-9460-45b7-9ce6-7ed33be7eb2c',
 				});
-				return;
 			}
 
 			const clientDataJSON = Buffer.from(body.clientDataJSON, 'hex');
@@ -179,10 +184,9 @@ export class SigninApiService {
 			});
 
 			if (!challenge) {
-				await fail(403, {
+				return await fail(403, {
 					id: '2715a88a-2125-4013-932f-aa6fe72792da',
 				});
-				return;
 			}
 
 			await this.attestationChallengesRepository.delete({
@@ -191,10 +195,9 @@ export class SigninApiService {
 			});
 
 			if (new Date().getTime() - challenge.createdAt.getTime() >= 5 * 60 * 1000) {
-				await fail(403, {
+				return await fail(403, {
 					id: '2715a88a-2125-4013-932f-aa6fe72792da',
 				});
-				return;
 			}
 
 			const securityKey = await this.userSecurityKeysRepository.findOneBy({
@@ -207,10 +210,9 @@ export class SigninApiService {
 			});
 
 			if (!securityKey) {
-				await fail(403, {
+				return await fail(403, {
 					id: '66269679-aeaf-4474-862b-eb761197e046',
 				});
-				return;
 			}
 
 			const isValid = this.twoFactorAuthenticationService.verifySignin({
@@ -223,20 +225,17 @@ export class SigninApiService {
 			});
 
 			if (isValid) {
-				this.signinService.signin(ctx, user);
-				return;
+				return this.signinService.signin(request, reply, user);
 			} else {
-				await fail(403, {
+				return await fail(403, {
 					id: '93b86c4b-72f9-40eb-9815-798928603d1e',
 				});
-				return;
 			}
 		} else {
 			if (!same && !profile.usePasswordLessLogin) {
-				await fail(403, {
+				return await fail(403, {
 					id: '932c904e-9460-45b7-9ce6-7ed33be7eb2c',
 				});
-				return;
 			}
 
 			const keys = await this.userSecurityKeysRepository.findBy({
@@ -244,10 +243,9 @@ export class SigninApiService {
 			});
 
 			if (keys.length === 0) {
-				await fail(403, {
+				return await fail(403, {
 					id: 'f27fd449-9af4-4841-9249-1f989b9fa4a4',
 				});
-				return;
 			}
 
 			// 32 byte challenge
@@ -266,15 +264,14 @@ export class SigninApiService {
 				registrationChallenge: false,
 			});
 
-			ctx.body = {
+			reply.code(200);
+			return {
 				challenge,
 				challengeId,
 				securityKeys: keys.map(key => ({
 					id: key.id,
 				})),
 			};
-			ctx.status = 200;
-			return;
 		}
 	// never get here
 	}
diff --git a/packages/backend/src/server/api/SigninService.ts b/packages/backend/src/server/api/SigninService.ts
index 3b96dfee6f..18a1d6c088 100644
--- a/packages/backend/src/server/api/SigninService.ts
+++ b/packages/backend/src/server/api/SigninService.ts
@@ -1,13 +1,12 @@
 import { Inject, Injectable } from '@nestjs/common';
+import { FastifyInstance, FastifyRequest, FastifyReply } from 'fastify';
 import { DI } from '@/di-symbols.js';
-import type { SigninsRepository } from '@/models/index.js';
-import type { UsersRepository } from '@/models/index.js';
+import type { SigninsRepository, UsersRepository } from '@/models/index.js';
 import type { Config } from '@/config.js';
 import { IdService } from '@/core/IdService.js';
 import type { ILocalUser } from '@/models/entities/User.js';
 import { GlobalEventService } from '@/core/GlobalEventService.js';
 import { SigninEntityService } from '@/core/entities/SigninEntityService.js';
-import type Koa from 'koa';
 
 @Injectable()
 export class SigninService {
@@ -24,10 +23,25 @@ export class SigninService {
 	) {
 	}
 
-	public signin(ctx: Koa.Context, user: ILocalUser, redirect = false) {
+	public signin(request: FastifyRequest, reply: FastifyReply, user: ILocalUser, redirect = false) {
+		setImmediate(async () => {
+			// Append signin history
+			const record = await this.signinsRepository.insert({
+				id: this.idService.genId(),
+				createdAt: new Date(),
+				userId: user.id,
+				ip: request.ip,
+				headers: request.headers,
+				success: true,
+			}).then(x => this.signinsRepository.findOneByOrFail(x.identifiers[0]));
+	
+			// Publish signin event
+			this.globalEventService.publishMainStream(user.id, 'signin', await this.signinEntityService.pack(record));
+		});
+
 		if (redirect) {
 			//#region Cookie
-			ctx.cookies.set('igi', user.token!, {
+			reply.cookies.set('igi', user.token!, {
 				path: '/',
 				// SEE: https://github.com/koajs/koa/issues/974
 				// When using a SSL proxy it should be configured to add the "X-Forwarded-Proto: https" header
@@ -36,29 +50,14 @@ export class SigninService {
 			});
 			//#endregion
 	
-			ctx.redirect(this.config.url);
+			reply.redirect(this.config.url);
 		} else {
-			ctx.body = {
+			reply.code(200);
+			return {
 				id: user.id,
 				i: user.token,
 			};
-			ctx.status = 200;
 		}
-	
-		(async () => {
-			// Append signin history
-			const record = await this.signinsRepository.insert({
-				id: this.idService.genId(),
-				createdAt: new Date(),
-				userId: user.id,
-				ip: ctx.ip,
-				headers: ctx.headers,
-				success: true,
-			}).then(x => this.signinsRepository.findOneByOrFail(x.identifiers[0]));
-	
-			// Publish signin event
-			this.globalEventService.publishMainStream(user.id, 'signin', await this.signinEntityService.pack(record));
-		})();
 	}
 }
 
diff --git a/packages/backend/src/server/api/SignupApiService.ts b/packages/backend/src/server/api/SignupApiService.ts
index edb8e4e8e6..771858d091 100644
--- a/packages/backend/src/server/api/SignupApiService.ts
+++ b/packages/backend/src/server/api/SignupApiService.ts
@@ -1,6 +1,7 @@
 import { Inject, Injectable } from '@nestjs/common';
 import rndstr from 'rndstr';
 import bcrypt from 'bcryptjs';
+import { FastifyInstance, FastifyRequest, FastifyReply } from 'fastify';
 import { DI } from '@/di-symbols.js';
 import type { RegistrationTicketsRepository, UserPendingsRepository, UserProfilesRepository, UsersRepository } from '@/models/index.js';
 import type { Config } from '@/config.js';
@@ -11,8 +12,8 @@ import { SignupService } from '@/core/SignupService.js';
 import { UserEntityService } from '@/core/entities/UserEntityService.js';
 import { EmailService } from '@/core/EmailService.js';
 import { ILocalUser } from '@/models/entities/User.js';
+import { FastifyReplyError } from '@/misc/fastify-reply-error.js';
 import { SigninService } from './SigninService.js';
-import type Koa from 'koa';
 
 @Injectable()
 export class SignupApiService {
@@ -42,8 +43,22 @@ export class SignupApiService {
 	) {
 	}
 
-	public async signup(ctx: Koa.Context) {
-		const body = ctx.request.body;
+	public async signup(
+		request: FastifyRequest<{
+			Body: {
+				username: string;
+				password: string;
+				host?: string;
+				invitationCode?: string;
+				emailAddress?: string;
+				'hcaptcha-response'?: string;
+				'g-recaptcha-response'?: string;
+				'turnstile-response'?: string;
+			}
+		}>,
+		reply: FastifyReply,
+	) {
+		const body = request.body;
 
 		const instance = await this.metaService.fetch(true);
 	
@@ -51,20 +66,20 @@ export class SignupApiService {
 		// ただしテスト時はこの機構は障害となるため無効にする
 		if (process.env.NODE_ENV !== 'test') {
 			if (instance.enableHcaptcha && instance.hcaptchaSecretKey) {
-				await this.captchaService.verifyHcaptcha(instance.hcaptchaSecretKey, body['hcaptcha-response']).catch(e => {
-					ctx.throw(400, e);
+				await this.captchaService.verifyHcaptcha(instance.hcaptchaSecretKey, body['hcaptcha-response']).catch(err => {
+					throw new FastifyReplyError(400, err);
 				});
 			}
 	
 			if (instance.enableRecaptcha && instance.recaptchaSecretKey) {
-				await this.captchaService.verifyRecaptcha(instance.recaptchaSecretKey, body['g-recaptcha-response']).catch(e => {
-					ctx.throw(400, e);
+				await this.captchaService.verifyRecaptcha(instance.recaptchaSecretKey, body['g-recaptcha-response']).catch(err => {
+					throw new FastifyReplyError(400, err);
 				});
 			}
 
 			if (instance.enableTurnstile && instance.turnstileSecretKey) {
-				await this.captchaService.verifyTurnstile(instance.turnstileSecretKey, body['turnstile-response']).catch(e => {
-					ctx.throw(400, e);
+				await this.captchaService.verifyTurnstile(instance.turnstileSecretKey, body['turnstile-response']).catch(err => {
+					throw new FastifyReplyError(400, err);
 				});
 			}
 		}
@@ -77,20 +92,20 @@ export class SignupApiService {
 	
 		if (instance.emailRequiredForSignup) {
 			if (emailAddress == null || typeof emailAddress !== 'string') {
-				ctx.status = 400;
+				reply.code(400);
 				return;
 			}
 	
-			const available = await this.emailService.validateEmailForAccount(emailAddress);
-			if (!available) {
-				ctx.status = 400;
+			const res = await this.emailService.validateEmailForAccount(emailAddress);
+			if (!res.available) {
+				reply.code(400);
 				return;
 			}
 		}
 	
 		if (instance.disableRegistration) {
 			if (invitationCode == null || typeof invitationCode !== 'string') {
-				ctx.status = 400;
+				reply.code(400);
 				return;
 			}
 	
@@ -99,7 +114,7 @@ export class SignupApiService {
 			});
 	
 			if (ticket == null) {
-				ctx.status = 400;
+				reply.code(400);
 				return;
 			}
 	
@@ -117,18 +132,18 @@ export class SignupApiService {
 				id: this.idService.genId(),
 				createdAt: new Date(),
 				code,
-				email: emailAddress,
+				email: emailAddress!,
 				username: username,
 				password: hash,
 			});
 	
 			const link = `${this.config.url}/signup-complete/${code}`;
 	
-			this.emailService.sendEmail(emailAddress, 'Signup',
+			this.emailService.sendEmail(emailAddress!, 'Signup',
 				`To complete signup, please click this link:<br><a href="${link}">${link}</a>`,
 				`To complete signup, please click this link: ${link}`);
 	
-			ctx.status = 204;
+			reply.code(204);
 		} else {
 			try {
 				const { account, secret } = await this.signupService.signup({
@@ -140,17 +155,18 @@ export class SignupApiService {
 					includeSecrets: true,
 				});
 	
-				(res as any).token = secret;
-	
-				ctx.body = res;
-			} catch (e) {
-				ctx.throw(400, e);
+				return {
+					...res,
+					token: secret,
+				};
+			} catch (err) {
+				throw new FastifyReplyError(400, err);
 			}
 		}
 	}
 
-	public async signupPending(ctx: Koa.Context) {
-		const body = ctx.request.body;
+	public async signupPending(request: FastifyRequest<{ Body: { code: string; } }>, reply: FastifyReply) {
+		const body = request.body;
 
 		const code = body['code'];
 
@@ -174,9 +190,9 @@ export class SignupApiService {
 				emailVerifyCode: null,
 			});
 
-			this.signinService.signin(ctx, account as ILocalUser);
-		} catch (e) {
-			ctx.throw(400, e);
+			this.signinService.signin(request, reply, account as ILocalUser);
+		} catch (err) {
+			throw new FastifyReplyError(400, err);
 		}
 	}
 }
diff --git a/packages/backend/src/server/api/endpoint-base.ts b/packages/backend/src/server/api/endpoint-base.ts
index 0a7f9b3008..b27329b9a9 100644
--- a/packages/backend/src/server/api/endpoint-base.ts
+++ b/packages/backend/src/server/api/endpoint-base.ts
@@ -14,23 +14,28 @@ ajv.addFormat('misskey:id', /^[a-zA-Z0-9]+$/);
 
 export type Response = Record<string, any> | void;
 
+type File = {
+	name: string | null;
+	path: string;
+};
+
 // TODO: paramsの型をT['params']のスキーマ定義から推論する
 type executor<T extends IEndpointMeta, Ps extends Schema> =
-	(params: SchemaType<Ps>, user: T['requireCredential'] extends true ? CacheableLocalUser : CacheableLocalUser | null, token: AccessToken | null, file?: any, cleanup?: () => any, ip?: string | null, headers?: Record<string, string> | null) =>
+	(params: SchemaType<Ps>, user: T['requireCredential'] extends true ? CacheableLocalUser : CacheableLocalUser | null, token: AccessToken | null, file?: File, cleanup?: () => any, ip?: string | null, headers?: Record<string, string> | null) =>
 		Promise<T['res'] extends undefined ? Response : SchemaType<NonNullable<T['res']>>>;
 
 export abstract class Endpoint<T extends IEndpointMeta, Ps extends Schema> {
-	public exec: (params: any, user: T['requireCredential'] extends true ? CacheableLocalUser : CacheableLocalUser | null, token: AccessToken | null, file?: any, ip?: string | null, headers?: Record<string, string> | null) => Promise<any>;
+	public exec: (params: any, user: T['requireCredential'] extends true ? CacheableLocalUser : CacheableLocalUser | null, token: AccessToken | null, file?: File, ip?: string | null, headers?: Record<string, string> | null) => Promise<any>;
 
 	constructor(meta: T, paramDef: Ps, cb: executor<T, Ps>) {
 		const validate = ajv.compile(paramDef);
 
-		this.exec = (params: any, user: T['requireCredential'] extends true ? CacheableLocalUser : CacheableLocalUser | null, token: AccessToken | null, file?: any, ip?: string | null, headers?: Record<string, string> | null) => {
+		this.exec = (params: any, user: T['requireCredential'] extends true ? CacheableLocalUser : CacheableLocalUser | null, token: AccessToken | null, file?: File, ip?: string | null, headers?: Record<string, string> | null) => {
 			let cleanup: undefined | (() => void) = undefined;
 	
 			if (meta.requireFile) {
 				cleanup = () => {
-					fs.unlink(file.path, () => {});
+					if (file) fs.unlink(file.path, () => {});
 				};
 	
 				if (file == null) return Promise.reject(new ApiError({
diff --git a/packages/backend/src/server/api/endpoints/drive/files/create.ts b/packages/backend/src/server/api/endpoints/drive/files/create.ts
index d394f5c3da..3f4485fc8b 100644
--- a/packages/backend/src/server/api/endpoints/drive/files/create.ts
+++ b/packages/backend/src/server/api/endpoints/drive/files/create.ts
@@ -78,8 +78,8 @@ export default class extends Endpoint<typeof meta, typeof paramDef> {
 	) {
 		super(meta, paramDef, async (ps, me, _, file, cleanup, ip, headers) => {
 			// Get 'name' parameter
-			let name = ps.name ?? file.originalname;
-			if (name !== undefined && name !== null) {
+			let name = ps.name ?? file!.name ?? null;
+			if (name != null) {
 				name = name.trim();
 				if (name.length === 0) {
 					name = null;
@@ -88,8 +88,6 @@ export default class extends Endpoint<typeof meta, typeof paramDef> {
 				} else if (!this.driveFileEntityService.validateFileName(name)) {
 					throw new ApiError(meta.errors.invalidFileName);
 				}
-			} else {
-				name = null;
 			}
 
 			const meta = await this.metaService.fetch();
@@ -98,7 +96,7 @@ export default class extends Endpoint<typeof meta, typeof paramDef> {
 				// Create file
 				const driveFile = await this.driveService.addFile({
 					user: me,
-					path: file.path,
+					path: file!.path,
 					name,
 					comment: ps.comment,
 					folderId: ps.folderId,
diff --git a/packages/backend/src/server/api/integration/DiscordServerService.ts b/packages/backend/src/server/api/integration/DiscordServerService.ts
index 1fd103797c..93c22a6c0b 100644
--- a/packages/backend/src/server/api/integration/DiscordServerService.ts
+++ b/packages/backend/src/server/api/integration/DiscordServerService.ts
@@ -1,9 +1,9 @@
 import { Inject, Injectable } from '@nestjs/common';
 import Redis from 'ioredis';
-import Router from '@koa/router';
 import { OAuth2 } from 'oauth';
 import { v4 as uuid } from 'uuid';
 import { IsNull } from 'typeorm';
+import { FastifyInstance, FastifyRequest, FastifyReply, FastifyPluginOptions } from 'fastify';
 import type { Config } from '@/config.js';
 import type { UserProfilesRepository, UsersRepository } from '@/models/index.js';
 import { DI } from '@/di-symbols.js';
@@ -12,8 +12,8 @@ import type { ILocalUser } from '@/models/entities/User.js';
 import { GlobalEventService } from '@/core/GlobalEventService.js';
 import { MetaService } from '@/core/MetaService.js';
 import { UserEntityService } from '@/core/entities/UserEntityService.js';
+import { FastifyReplyError } from '@/misc/fastify-reply-error.js';
 import { SigninService } from '../SigninService.js';
-import type Koa from 'koa';
 
 @Injectable()
 export class DiscordServerService {
@@ -36,21 +36,18 @@ export class DiscordServerService {
 		private metaService: MetaService,
 		private signinService: SigninService,
 	) {
+		this.create = this.create.bind(this);
 	}
 
-	public create() {
-		const router = new Router();
-
-		router.get('/disconnect/discord', async ctx => {
-			if (!this.compareOrigin(ctx)) {
-				ctx.throw(400, 'invalid origin');
-				return;
+	public create(fastify: FastifyInstance, options: FastifyPluginOptions, done: (err?: Error) => void) {
+		fastify.get('/disconnect/discord', async (request, reply) => {
+			if (!this.compareOrigin(request)) {
+				throw new FastifyReplyError(400, 'invalid origin');
 			}
 
-			const userToken = this.getUserToken(ctx);
+			const userToken = this.getUserToken(request);
 			if (!userToken) {
-				ctx.throw(400, 'signin required');
-				return;
+				throw new FastifyReplyError(400, 'signin required');
 			}
 
 			const user = await this.usersRepository.findOneByOrFail({
@@ -66,13 +63,13 @@ export class DiscordServerService {
 				integrations: profile.integrations,
 			});
 
-			ctx.body = 'Discordの連携を解除しました :v:';
-
 			// Publish i updated event
 			this.globalEventService.publishMainStream(user.id, 'meUpdated', await this.userEntityService.pack(user, user, {
 				detail: true,
 				includeSecrets: true,
 			}));
+
+			return 'Discordの連携を解除しました :v:';
 		});
 
 		const getOAuth2 = async () => {
@@ -90,16 +87,14 @@ export class DiscordServerService {
 			}
 		};
 
-		router.get('/connect/discord', async ctx => {
-			if (!this.compareOrigin(ctx)) {
-				ctx.throw(400, 'invalid origin');
-				return;
+		fastify.get('/connect/discord', async (request, reply) => {
+			if (!this.compareOrigin(request)) {
+				throw new FastifyReplyError(400, 'invalid origin');
 			}
 
-			const userToken = this.getUserToken(ctx);
+			const userToken = this.getUserToken(request);
 			if (!userToken) {
-				ctx.throw(400, 'signin required');
-				return;
+				throw new FastifyReplyError(400, 'signin required');
 			}
 
 			const params = {
@@ -112,10 +107,10 @@ export class DiscordServerService {
 			this.redisClient.set(userToken, JSON.stringify(params));
 
 			const oauth2 = await getOAuth2();
-			ctx.redirect(oauth2!.getAuthorizeUrl(params));
+			reply.redirect(oauth2!.getAuthorizeUrl(params));
 		});
 
-		router.get('/signin/discord', async ctx => {
+		fastify.get('/signin/discord', async (request, reply) => {
 			const sessid = uuid();
 
 			const params = {
@@ -125,7 +120,7 @@ export class DiscordServerService {
 				response_type: 'code',
 			};
 
-			ctx.cookies.set('signin_with_discord_sid', sessid, {
+			reply.cookies.set('signin_with_discord_sid', sessid, {
 				path: '/',
 				secure: this.config.url.startsWith('https'),
 				httpOnly: true,
@@ -134,27 +129,25 @@ export class DiscordServerService {
 			this.redisClient.set(sessid, JSON.stringify(params));
 
 			const oauth2 = await getOAuth2();
-			ctx.redirect(oauth2!.getAuthorizeUrl(params));
+			reply.redirect(oauth2!.getAuthorizeUrl(params));
 		});
 
-		router.get('/dc/cb', async ctx => {
-			const userToken = this.getUserToken(ctx);
+		fastify.get('/dc/cb', async (request, reply) => {
+			const userToken = this.getUserToken(request);
 
 			const oauth2 = await getOAuth2();
 
 			if (!userToken) {
-				const sessid = ctx.cookies.get('signin_with_discord_sid');
+				const sessid = request.cookies.get('signin_with_discord_sid');
 
 				if (!sessid) {
-					ctx.throw(400, 'invalid session');
-					return;
+					throw new FastifyReplyError(400, 'invalid session');
 				}
 
-				const code = ctx.query.code;
+				const code = request.query.code;
 
 				if (!code || typeof code !== 'string') {
-					ctx.throw(400, 'invalid session');
-					return;
+					throw new FastifyReplyError(400, 'invalid session');
 				}
 
 				const { redirect_uri, state } = await new Promise<any>((res, rej) => {
@@ -164,9 +157,8 @@ export class DiscordServerService {
 					});
 				});
 
-				if (ctx.query.state !== state) {
-					ctx.throw(400, 'invalid session');
-					return;
+				if (request.query.state !== state) {
+					throw new FastifyReplyError(400, 'invalid session');
 				}
 
 				const { accessToken, refreshToken, expiresDate } = await new Promise<any>((res, rej) =>
@@ -192,8 +184,7 @@ export class DiscordServerService {
 				})) as Record<string, unknown>;
 
 				if (typeof id !== 'string' || typeof username !== 'string' || typeof discriminator !== 'string') {
-					ctx.throw(400, 'invalid session');
-					return;
+					throw new FastifyReplyError(400, 'invalid session');
 				}
 
 				const profile = await this.userProfilesRepository.createQueryBuilder()
@@ -202,8 +193,7 @@ export class DiscordServerService {
 					.getOne();
 
 				if (profile == null) {
-					ctx.throw(404, `@${username}#${discriminator}と連携しているMisskeyアカウントはありませんでした...`);
-					return;
+					throw new FastifyReplyError(404, `@${username}#${discriminator}と連携しているMisskeyアカウントはありませんでした...`);
 				}
 
 				await this.userProfilesRepository.update(profile.userId, {
@@ -220,13 +210,12 @@ export class DiscordServerService {
 					},
 				});
 
-				this.signinService.signin(ctx, await this.usersRepository.findOneBy({ id: profile.userId }) as ILocalUser, true);
+				return this.signinService.signin(request, reply, await this.usersRepository.findOneBy({ id: profile.userId }) as ILocalUser, true);
 			} else {
-				const code = ctx.query.code;
+				const code = request.query.code;
 
 				if (!code || typeof code !== 'string') {
-					ctx.throw(400, 'invalid session');
-					return;
+					throw new FastifyReplyError(400, 'invalid session');
 				}
 
 				const { redirect_uri, state } = await new Promise<any>((res, rej) => {
@@ -236,9 +225,8 @@ export class DiscordServerService {
 					});
 				});
 
-				if (ctx.query.state !== state) {
-					ctx.throw(400, 'invalid session');
-					return;
+				if (request.query.state !== state) {
+					throw new FastifyReplyError(400, 'invalid session');
 				}
 
 				const { accessToken, refreshToken, expiresDate } = await new Promise<any>((res, rej) =>
@@ -263,8 +251,7 @@ export class DiscordServerService {
 					'Authorization': `Bearer ${accessToken}`,
 				})) as Record<string, unknown>;
 				if (typeof id !== 'string' || typeof username !== 'string' || typeof discriminator !== 'string') {
-					ctx.throw(400, 'invalid session');
-					return;
+					throw new FastifyReplyError(400, 'invalid session');
 				}
 
 				const user = await this.usersRepository.findOneByOrFail({
@@ -288,29 +275,29 @@ export class DiscordServerService {
 					},
 				});
 
-				ctx.body = `Discord: @${username}#${discriminator} を、Misskey: @${user.username} に接続しました！`;
-
 				// Publish i updated event
 				this.globalEventService.publishMainStream(user.id, 'meUpdated', await this.userEntityService.pack(user, user, {
 					detail: true,
 					includeSecrets: true,
 				}));
+
+				return `Discord: @${username}#${discriminator} を、Misskey: @${user.username} に接続しました！`;
 			}
 		});
 
-		return router;
+		done();
 	}
 
-	private getUserToken(ctx: Koa.BaseContext): string | null {
-		return ((ctx.headers['cookie'] ?? '').match(/igi=(\w+)/) ?? [null, null])[1];
+	private getUserToken(request: FastifyRequest): string | null {
+		return ((request.headers['cookie'] ?? '').match(/igi=(\w+)/) ?? [null, null])[1];
 	}
 	
-	private compareOrigin(ctx: Koa.BaseContext): boolean {
+	private compareOrigin(request: FastifyRequest): boolean {
 		function normalizeUrl(url?: string): string {
 			return url ? url.endsWith('/') ? url.substr(0, url.length - 1) : url : '';
 		}
 	
-		const referer = ctx.headers['referer'];
+		const referer = request.headers['referer'];
 	
 		return (normalizeUrl(referer) === normalizeUrl(this.config.url));
 	}
diff --git a/packages/backend/src/server/api/integration/GithubServerService.ts b/packages/backend/src/server/api/integration/GithubServerService.ts
index 98d6230749..2fd20bf831 100644
--- a/packages/backend/src/server/api/integration/GithubServerService.ts
+++ b/packages/backend/src/server/api/integration/GithubServerService.ts
@@ -1,9 +1,9 @@
 import { Inject, Injectable } from '@nestjs/common';
 import Redis from 'ioredis';
-import Router from '@koa/router';
 import { OAuth2 } from 'oauth';
 import { v4 as uuid } from 'uuid';
 import { IsNull } from 'typeorm';
+import { FastifyInstance, FastifyRequest, FastifyReply, FastifyPluginOptions } from 'fastify';
 import type { Config } from '@/config.js';
 import type { UserProfilesRepository, UsersRepository } from '@/models/index.js';
 import { DI } from '@/di-symbols.js';
@@ -12,8 +12,8 @@ import type { ILocalUser } from '@/models/entities/User.js';
 import { GlobalEventService } from '@/core/GlobalEventService.js';
 import { MetaService } from '@/core/MetaService.js';
 import { UserEntityService } from '@/core/entities/UserEntityService.js';
+import { FastifyReplyError } from '@/misc/fastify-reply-error.js';
 import { SigninService } from '../SigninService.js';
-import type Koa from 'koa';
 
 @Injectable()
 export class GithubServerService {
@@ -36,21 +36,18 @@ export class GithubServerService {
 		private metaService: MetaService,
 		private signinService: SigninService,
 	) {
+		this.create = this.create.bind(this);
 	}
 
-	public create() {
-		const router = new Router();
-
-		router.get('/disconnect/github', async ctx => {
-			if (!this.compareOrigin(ctx)) {
-				ctx.throw(400, 'invalid origin');
-				return;
+	public create(fastify: FastifyInstance, options: FastifyPluginOptions, done: (err?: Error) => void) {
+		fastify.get('/disconnect/github', async (request, reply) => {
+			if (!this.compareOrigin(request)) {
+				throw new FastifyReplyError(400, 'invalid origin');
 			}
 
-			const userToken = this.getUserToken(ctx);
+			const userToken = this.getUserToken(request);
 			if (!userToken) {
-				ctx.throw(400, 'signin required');
-				return;
+				throw new FastifyReplyError(400, 'signin required');
 			}
 
 			const user = await this.usersRepository.findOneByOrFail({
@@ -66,13 +63,13 @@ export class GithubServerService {
 				integrations: profile.integrations,
 			});
 
-			ctx.body = 'GitHubの連携を解除しました :v:';
-
 			// Publish i updated event
 			this.globalEventService.publishMainStream(user.id, 'meUpdated', await this.userEntityService.pack(user, user, {
 				detail: true,
 				includeSecrets: true,
 			}));
+
+			return 'GitHubの連携を解除しました :v:';
 		});
 
 		const getOath2 = async () => {
@@ -90,16 +87,14 @@ export class GithubServerService {
 			}
 		};
 
-		router.get('/connect/github', async ctx => {
-			if (!this.compareOrigin(ctx)) {
-				ctx.throw(400, 'invalid origin');
-				return;
+		fastify.get('/connect/github', async (request, reply) => {
+			if (!this.compareOrigin(request)) {
+				throw new FastifyReplyError(400, 'invalid origin');
 			}
 
-			const userToken = this.getUserToken(ctx);
+			const userToken = this.getUserToken(request);
 			if (!userToken) {
-				ctx.throw(400, 'signin required');
-				return;
+				throw new FastifyReplyError(400, 'signin required');
 			}
 
 			const params = {
@@ -111,10 +106,10 @@ export class GithubServerService {
 			this.redisClient.set(userToken, JSON.stringify(params));
 
 			const oauth2 = await getOath2();
-			ctx.redirect(oauth2!.getAuthorizeUrl(params));
+			reply.redirect(oauth2!.getAuthorizeUrl(params));
 		});
 
-		router.get('/signin/github', async ctx => {
+		fastify.get('/signin/github', async (request, reply) => {
 			const sessid = uuid();
 
 			const params = {
@@ -123,7 +118,7 @@ export class GithubServerService {
 				state: uuid(),
 			};
 
-			ctx.cookies.set('signin_with_github_sid', sessid, {
+			reply.cookies.set('signin_with_github_sid', sessid, {
 				path: '/',
 				secure: this.config.url.startsWith('https'),
 				httpOnly: true,
@@ -132,27 +127,25 @@ export class GithubServerService {
 			this.redisClient.set(sessid, JSON.stringify(params));
 
 			const oauth2 = await getOath2();
-			ctx.redirect(oauth2!.getAuthorizeUrl(params));
+			reply.redirect(oauth2!.getAuthorizeUrl(params));
 		});
 
-		router.get('/gh/cb', async ctx => {
-			const userToken = this.getUserToken(ctx);
+		fastify.get('/gh/cb', async (request, reply) => {
+			const userToken = this.getUserToken(request);
 
 			const oauth2 = await getOath2();
 
 			if (!userToken) {
-				const sessid = ctx.cookies.get('signin_with_github_sid');
+				const sessid = request.cookies.get('signin_with_github_sid');
 
 				if (!sessid) {
-					ctx.throw(400, 'invalid session');
-					return;
+					throw new FastifyReplyError(400, 'invalid session');
 				}
 
-				const code = ctx.query.code;
+				const code = request.query.code;
 
 				if (!code || typeof code !== 'string') {
-					ctx.throw(400, 'invalid session');
-					return;
+					throw new FastifyReplyError(400, 'invalid session');
 				}
 
 				const { redirect_uri, state } = await new Promise<any>((res, rej) => {
@@ -162,9 +155,8 @@ export class GithubServerService {
 					});
 				});
 
-				if (ctx.query.state !== state) {
-					ctx.throw(400, 'invalid session');
-					return;
+				if (request.query.state !== state) {
+					throw new FastifyReplyError(400, 'invalid session');
 				}
 
 				const { accessToken } = await new Promise<{ accessToken: string }>((res, rej) =>
@@ -184,8 +176,7 @@ export class GithubServerService {
 					'Authorization': `bearer ${accessToken}`,
 				})) as Record<string, unknown>;
 				if (typeof login !== 'string' || typeof id !== 'string') {
-					ctx.throw(400, 'invalid session');
-					return;
+					throw new FastifyReplyError(400, 'invalid session');
 				}
 
 				const link = await this.userProfilesRepository.createQueryBuilder()
@@ -194,17 +185,15 @@ export class GithubServerService {
 					.getOne();
 
 				if (link == null) {
-					ctx.throw(404, `@${login}と連携しているMisskeyアカウントはありませんでした...`);
-					return;
+					throw new FastifyReplyError(404, `@${login}と連携しているMisskeyアカウントはありませんでした...`);
 				}
 
-				this.signinService.signin(ctx, await this.usersRepository.findOneBy({ id: link.userId }) as ILocalUser, true);
+				return this.signinService.signin(request, reply, await this.usersRepository.findOneBy({ id: link.userId }) as ILocalUser, true);
 			} else {
-				const code = ctx.query.code;
+				const code = request.query.code;
 
 				if (!code || typeof code !== 'string') {
-					ctx.throw(400, 'invalid session');
-					return;
+					throw new FastifyReplyError(400, 'invalid session');
 				}
 
 				const { redirect_uri, state } = await new Promise<any>((res, rej) => {
@@ -214,9 +203,8 @@ export class GithubServerService {
 					});
 				});
 
-				if (ctx.query.state !== state) {
-					ctx.throw(400, 'invalid session');
-					return;
+				if (request.query.state !== state) {
+					throw new FastifyReplyError(400, 'invalid session');
 				}
 
 				const { accessToken } = await new Promise<{ accessToken: string }>((res, rej) =>
@@ -238,8 +226,7 @@ export class GithubServerService {
 				})) as Record<string, unknown>;
 
 				if (typeof login !== 'string' || typeof id !== 'string') {
-					ctx.throw(400, 'invalid session');
-					return;
+					throw new FastifyReplyError(400, 'invalid session');
 				}
 
 				const user = await this.usersRepository.findOneByOrFail({
@@ -260,29 +247,29 @@ export class GithubServerService {
 					},
 				});
 
-				ctx.body = `GitHub: @${login} を、Misskey: @${user.username} に接続しました！`;
-
 				// Publish i updated event
 				this.globalEventService.publishMainStream(user.id, 'meUpdated', await this.userEntityService.pack(user, user, {
 					detail: true,
 					includeSecrets: true,
 				}));
+
+				return `GitHub: @${login} を、Misskey: @${user.username} に接続しました！`;
 			}
 		});
 
-		return router;
+		done();
 	}
 
-	private getUserToken(ctx: Koa.BaseContext): string | null {
-		return ((ctx.headers['cookie'] ?? '').match(/igi=(\w+)/) ?? [null, null])[1];
+	private getUserToken(request: FastifyRequest): string | null {
+		return ((request.headers['cookie'] ?? '').match(/igi=(\w+)/) ?? [null, null])[1];
 	}
 	
-	private compareOrigin(ctx: Koa.BaseContext): boolean {
+	private compareOrigin(request: FastifyRequest): boolean {
 		function normalizeUrl(url?: string): string {
 			return url ? url.endsWith('/') ? url.substr(0, url.length - 1) : url : '';
 		}
 	
-		const referer = ctx.headers['referer'];
+		const referer = request.headers['referer'];
 	
 		return (normalizeUrl(referer) === normalizeUrl(this.config.url));
 	}
diff --git a/packages/backend/src/server/api/integration/TwitterServerService.ts b/packages/backend/src/server/api/integration/TwitterServerService.ts
index 57c977bc54..a8447f9d49 100644
--- a/packages/backend/src/server/api/integration/TwitterServerService.ts
+++ b/packages/backend/src/server/api/integration/TwitterServerService.ts
@@ -1,6 +1,6 @@
 import { Inject, Injectable } from '@nestjs/common';
 import Redis from 'ioredis';
-import Router from '@koa/router';
+import { FastifyInstance, FastifyRequest, FastifyReply, FastifyPluginOptions } from 'fastify';
 import { v4 as uuid } from 'uuid';
 import { IsNull } from 'typeorm';
 import autwh from 'autwh';
@@ -12,8 +12,8 @@ import type { ILocalUser } from '@/models/entities/User.js';
 import { GlobalEventService } from '@/core/GlobalEventService.js';
 import { MetaService } from '@/core/MetaService.js';
 import { UserEntityService } from '@/core/entities/UserEntityService.js';
+import { FastifyReplyError } from '@/misc/fastify-reply-error.js';
 import { SigninService } from '../SigninService.js';
-import type Koa from 'koa';
 
 @Injectable()
 export class TwitterServerService {
@@ -36,21 +36,18 @@ export class TwitterServerService {
 		private metaService: MetaService,
 		private signinService: SigninService,
 	) {
+		this.create = this.create.bind(this);
 	}
 
-	public create() {
-		const router = new Router();
-
-		router.get('/disconnect/twitter', async ctx => {
-			if (!this.compareOrigin(ctx)) {
-				ctx.throw(400, 'invalid origin');
-				return;
+	public create(fastify: FastifyInstance, options: FastifyPluginOptions, done: (err?: Error) => void) {
+		fastify.get('/disconnect/twitter', async (request, reply) => {
+			if (!this.compareOrigin(request)) {
+				throw new FastifyReplyError(400, 'invalid origin');
 			}
 
-			const userToken = this.getUserToken(ctx);
+			const userToken = this.getUserToken(request);
 			if (userToken == null) {
-				ctx.throw(400, 'signin required');
-				return;
+				throw new FastifyReplyError(400, 'signin required');
 			}
 
 			const user = await this.usersRepository.findOneByOrFail({
@@ -66,13 +63,13 @@ export class TwitterServerService {
 				integrations: profile.integrations,
 			});
 
-			ctx.body = 'Twitterの連携を解除しました :v:';
-
 			// Publish i updated event
 			this.globalEventService.publishMainStream(user.id, 'meUpdated', await this.userEntityService.pack(user, user, {
 				detail: true,
 				includeSecrets: true,
 			}));
+
+			return 'Twitterの連携を解除しました :v:';
 		});
 
 		const getTwAuth = async () => {
@@ -89,25 +86,23 @@ export class TwitterServerService {
 			}
 		};
 
-		router.get('/connect/twitter', async ctx => {
-			if (!this.compareOrigin(ctx)) {
-				ctx.throw(400, 'invalid origin');
-				return;
+		fastify.get('/connect/twitter', async (request, reply) => {
+			if (!this.compareOrigin(request)) {
+				throw new FastifyReplyError(400, 'invalid origin');
 			}
 
-			const userToken = this.getUserToken(ctx);
+			const userToken = this.getUserToken(request);
 			if (userToken == null) {
-				ctx.throw(400, 'signin required');
-				return;
+				throw new FastifyReplyError(400, 'signin required');
 			}
 
 			const twAuth = await getTwAuth();
 			const twCtx = await twAuth!.begin();
 			this.redisClient.set(userToken, JSON.stringify(twCtx));
-			ctx.redirect(twCtx.url);
+			reply.redirect(twCtx.url);
 		});
 
-		router.get('/signin/twitter', async ctx => {
+		fastify.get('/signin/twitter', async (request, reply) => {
 			const twAuth = await getTwAuth();
 			const twCtx = await twAuth!.begin();
 
@@ -115,26 +110,25 @@ export class TwitterServerService {
 
 			this.redisClient.set(sessid, JSON.stringify(twCtx));
 
-			ctx.cookies.set('signin_with_twitter_sid', sessid, {
+			reply.cookies.set('signin_with_twitter_sid', sessid, {
 				path: '/',
 				secure: this.config.url.startsWith('https'),
 				httpOnly: true,
 			});
 
-			ctx.redirect(twCtx.url);
+			reply.redirect(twCtx.url);
 		});
 
-		router.get('/tw/cb', async ctx => {
-			const userToken = this.getUserToken(ctx);
+		fastify.get('/tw/cb', async (request, reply) => {
+			const userToken = this.getUserToken(request);
 
 			const twAuth = await getTwAuth();
 
 			if (userToken == null) {
-				const sessid = ctx.cookies.get('signin_with_twitter_sid');
+				const sessid = request.cookies.get('signin_with_twitter_sid');
 
 				if (sessid == null) {
-					ctx.throw(400, 'invalid session');
-					return;
+					throw new FastifyReplyError(400, 'invalid session');
 				}
 
 				const get = new Promise<any>((res, rej) => {
@@ -145,10 +139,9 @@ export class TwitterServerService {
 
 				const twCtx = await get;
 
-				const verifier = ctx.query.oauth_verifier;
+				const verifier = request.query.oauth_verifier;
 				if (!verifier || typeof verifier !== 'string') {
-					ctx.throw(400, 'invalid session');
-					return;
+					throw new FastifyReplyError(400, 'invalid session');
 				}
 
 				const result = await twAuth!.done(JSON.parse(twCtx), verifier);
@@ -159,17 +152,15 @@ export class TwitterServerService {
 					.getOne();
 
 				if (link == null) {
-					ctx.throw(404, `@${result.screenName}と連携しているMisskeyアカウントはありませんでした...`);
-					return;
+					throw new FastifyReplyError(404, `@${result.screenName}と連携しているMisskeyアカウントはありませんでした...`);
 				}
 
-				this.signinService.signin(ctx, await this.usersRepository.findOneBy({ id: link.userId }) as ILocalUser, true);
+				return this.signinService.signin(request, reply, await this.usersRepository.findOneBy({ id: link.userId }) as ILocalUser, true);
 			} else {
-				const verifier = ctx.query.oauth_verifier;
+				const verifier = request.query.oauth_verifier;
 
 				if (!verifier || typeof verifier !== 'string') {
-					ctx.throw(400, 'invalid session');
-					return;
+					throw new FastifyReplyError(400, 'invalid session');
 				}
 
 				const get = new Promise<any>((res, rej) => {
@@ -201,29 +192,29 @@ export class TwitterServerService {
 					},
 				});
 
-				ctx.body = `Twitter: @${result.screenName} を、Misskey: @${user.username} に接続しました！`;
-
 				// Publish i updated event
 				this.globalEventService.publishMainStream(user.id, 'meUpdated', await this.userEntityService.pack(user, user, {
 					detail: true,
 					includeSecrets: true,
 				}));
+
+				return `Twitter: @${result.screenName} を、Misskey: @${user.username} に接続しました！`;
 			}
 		});
 
-		return router;
+		done();
 	}
 
-	private getUserToken(ctx: Koa.BaseContext): string | null {
-		return ((ctx.headers['cookie'] ?? '').match(/igi=(\w+)/) ?? [null, null])[1];
+	private getUserToken(request: FastifyRequest): string | null {
+		return ((request.headers['cookie'] ?? '').match(/igi=(\w+)/) ?? [null, null])[1];
 	}
 	
-	private compareOrigin(ctx: Koa.BaseContext): boolean {
+	private compareOrigin(request: FastifyRequest): boolean {
 		function normalizeUrl(url?: string): string {
 			return url ? url.endsWith('/') ? url.substr(0, url.length - 1) : url : '';
 		}
 	
-		const referer = ctx.headers['referer'];
+		const referer = request.headers['referer'];
 	
 		return (normalizeUrl(referer) === normalizeUrl(this.config.url));
 	}
diff --git a/packages/backend/src/server/web/ClientServerService.ts b/packages/backend/src/server/web/ClientServerService.ts
index 8957a91309..4c3f2bfd36 100644
--- a/packages/backend/src/server/web/ClientServerService.ts
+++ b/packages/backend/src/server/web/ClientServerService.ts
@@ -3,16 +3,12 @@ import { fileURLToPath } from 'node:url';
 import { PathOrFileDescriptor, readFileSync } from 'node:fs';
 import { Inject, Injectable } from '@nestjs/common';
 import ms from 'ms';
-import Koa from 'koa';
-import Router from '@koa/router';
-import send from 'koa-send';
-import favicon from 'koa-favicon';
-import views from 'koa-views';
 import sharp from 'sharp';
-import { createBullBoard } from '@bull-board/api';
-import { BullAdapter } from '@bull-board/api/bullAdapter.js';
-import { KoaAdapter } from '@bull-board/koa';
+import pug from 'pug';
 import { In, IsNull } from 'typeorm';
+import { FastifyInstance, FastifyPluginOptions, FastifyReply } from 'fastify';
+import fastifyStatic from '@fastify/static';
+import fastifyView from '@fastify/view';
 import type { Config } from '@/config.js';
 import { getNoteSummary } from '@/misc/get-note-summary.js';
 import { DI } from '@/di-symbols.js';
@@ -84,9 +80,10 @@ export class ClientServerService {
 		@Inject('queue:objectStorage') public objectStorageQueue: ObjectStorageQueue,
 		@Inject('queue:webhookDeliver') public webhookDeliverQueue: WebhookDeliverQueue,
 	) {
+		this.createServer = this.createServer.bind(this);
 	}
 
-	private async manifestHandler(ctx: Koa.Context) {
+	private async manifestHandler(reply: FastifyReply) {
 		const res = deepClone(manifest);
 
 		const instance = await this.metaService.fetch(true);
@@ -95,27 +92,26 @@ export class ClientServerService {
 		res.name = instance.name ?? 'Misskey';
 		if (instance.themeColor) res.theme_color = instance.themeColor;
 
-		ctx.set('Cache-Control', 'max-age=300');
-		ctx.body = res;
+		reply.header('Cache-Control', 'max-age=300');
+		return (res);
 	}
 
-	public createApp() {
-		const app = new Koa();
-
+	public createServer(fastify: FastifyInstance, options: FastifyPluginOptions, done: (err?: Error) => void) {
+		/* TODO
 		//#region Bull Dashboard
 		const bullBoardPath = '/queue';
 
 		// Authenticate
-		app.use(async (ctx, next) => {
+		app.use(async (request, reply) => {
 			if (ctx.path === bullBoardPath || ctx.path.startsWith(bullBoardPath + '/')) {
 				const token = ctx.cookies.get('token');
 				if (token == null) {
-					ctx.status = 401;
+					reply.code(401);
 					return;
 				}
 				const user = await this.usersRepository.findOneBy({ token });
 				if (user == null || !(user.isAdmin || user.isModerator)) {
-					ctx.status = 403;
+					reply.code(403);
 					return;
 				}
 			}
@@ -140,83 +136,84 @@ export class ClientServerService {
 		serverAdapter.setBasePath(bullBoardPath);
 		app.use(serverAdapter.registerPlugin());
 		//#endregion
+		*/
 
-		// Init renderer
-		app.use(views(_dirname + '/views', {
-			extension: 'pug',
-			options: {
+		fastify.register(fastifyView, {
+			root: _dirname + '/views',
+			engine: {
+				pug: pug,
+			},
+			defaultContext: {
 				version: this.config.version,
 				getClientEntry: () => process.env.NODE_ENV === 'production' ?
 					this.config.clientEntry :
 					JSON.parse(readFileSync(`${_dirname}/../../../../../built/_client_dist_/manifest.json`, 'utf-8'))['src/init.ts'],
 				config: this.config,
 			},
-		}));
-
-		// Serve favicon
-		app.use(favicon(`${_dirname}/../../../assets/favicon.ico`));
-
-		// Common request handler
-		app.use(async (ctx, next) => {
-			// IFrameの中に入れられないようにする
-			ctx.set('X-Frame-Options', 'DENY');
-			await next();
 		});
 
-		// Init router
-		const router = new Router();
+		fastify.addHook('onRequest', (request, reply, done) => {
+			// クリックジャッキング防止のためiFrameの中に入れられないようにする
+			reply.header('X-Frame-Options', 'DENY');
+			done();
+		});
 
 		//#region static assets
 
-		router.get('/static-assets/(.*)', async ctx => {
-			await send(ctx as any, ctx.path.replace('/static-assets/', ''), {
-				root: staticAssets,
-				maxage: ms('7 days'),
-			});
+		fastify.register(fastifyStatic, {
+			root: _dirname,
+			serve: false,
 		});
 
-		router.get('/client-assets/(.*)', async ctx => {
-			await send(ctx as any, ctx.path.replace('/client-assets/', ''), {
-				root: clientAssets,
-				maxage: ms('7 days'),
-			});
+		fastify.register(fastifyStatic, {
+			root: staticAssets,
+			prefix: '/static-assets/',
+			maxAge: ms('7 days'),
+			decorateReply: false,
 		});
 
-		router.get('/assets/(.*)', async ctx => {
-			await send(ctx as any, ctx.path.replace('/assets/', ''), {
-				root: assets,
-				maxage: ms('7 days'),
-			});
+		fastify.register(fastifyStatic, {
+			root: clientAssets,
+			prefix: '/client-assets/',
+			maxAge: ms('7 days'),
+			decorateReply: false,
 		});
 
-		// Apple touch icon
-		router.get('/apple-touch-icon.png', async ctx => {
-			await send(ctx as any, '/apple-touch-icon.png', {
-				root: staticAssets,
-			});
+		fastify.register(fastifyStatic, {
+			root: assets,
+			prefix: '/assets/',
+			maxAge: ms('7 days'),
+			decorateReply: false,
+		});
+
+		fastify.get('/favicon.ico', async (request, reply) => {
+			return reply.sendFile('/favicon.ico', staticAssets);
+		});
+
+		fastify.get('/apple-touch-icon.png', async (request, reply) => {
+			return reply.sendFile('/apple-touch-icon.png', staticAssets);
 		});
 
-		router.get('/twemoji/(.*)', async ctx => {
-			const path = ctx.path.replace('/twemoji/', '');
+		fastify.get<{ Params: { path: string } }>('/twemoji/:path(.*)', async (request, reply) => {
+			const path = request.params.path;
 
 			if (!path.match(/^[0-9a-f-]+\.svg$/)) {
-				ctx.status = 404;
+				reply.code(404);
 				return;
 			}
 
-			ctx.set('Content-Security-Policy', 'default-src \'none\'; style-src \'unsafe-inline\'');
+			reply.header('Content-Security-Policy', 'default-src \'none\'; style-src \'unsafe-inline\'');
 
-			await send(ctx as any, path, {
-				root: `${_dirname}/../../../node_modules/@discordapp/twemoji/dist/svg/`,
-				maxage: ms('30 days'),
+			return await reply.sendFile(path, `${_dirname}/../../../node_modules/@discordapp/twemoji/dist/svg/`, {
+				maxAge: ms('30 days'),
 			});
 		});
 
-		router.get('/twemoji-badge/(.*)', async ctx => {
-			const path = ctx.path.replace('/twemoji-badge/', '');
+		fastify.get<{ Params: { path: string } }>('/twemoji-badge/:path(.*)', async (request, reply) => {
+			const path = request.params.path;
 
 			if (!path.match(/^[0-9a-f-]+\.png$/)) {
-				ctx.status = 404;
+				reply.code(404);
 				return;
 			}
 
@@ -249,44 +246,43 @@ export class ClientServerService {
 				.png()
 				.toBuffer();
 
-			ctx.set('Content-Security-Policy', 'default-src \'none\'; style-src \'unsafe-inline\'');
-			ctx.set('Cache-Control', 'max-age=2592000');
-			ctx.set('Content-Type', 'image/png');
-			ctx.body = buffer;
+			reply.header('Content-Security-Policy', 'default-src \'none\'; style-src \'unsafe-inline\'');
+			reply.header('Cache-Control', 'max-age=2592000');
+			reply.header('Content-Type', 'image/png');
+			return buffer;
 		});
 
 		// ServiceWorker
-		router.get('/sw.js', async ctx => {
-			await send(ctx as any, '/sw.js', {
-				root: swAssets,
-				maxage: ms('10 minutes'),
+		fastify.get('/sw.js', async (request, reply) => {
+			return await reply.sendFile('/sw.js', swAssets, {
+				maxAge: ms('10 minutes'),
 			});
 		});
 
 		// Manifest
-		router.get('/manifest.json', ctx => this.manifestHandler(ctx));
+		fastify.get('/manifest.json', async (request, reply) => await this.manifestHandler(reply));
 
-		router.get('/robots.txt', async ctx => {
-			await send(ctx as any, '/robots.txt', {
-				root: staticAssets,
-			});
+		fastify.get('/robots.txt', async (request, reply) => {
+			return await reply.sendFile('/robots.txt', staticAssets);
 		});
 
 		//#endregion
 
-		// Docs
-		router.get('/api-doc', async ctx => {
-			await send(ctx as any, '/redoc.html', {
-				root: staticAssets,
+		const renderBase = async (reply: FastifyReply) => {
+			const meta = await this.metaService.fetch();
+			reply.header('Cache-Control', 'public, max-age=15');
+			return await reply.view('base', {
+				img: meta.bannerUrl,
+				title: meta.name ?? 'Misskey',
+				instanceName: meta.name ?? 'Misskey',
+				desc: meta.description,
+				icon: meta.iconUrl,
+				themeColor: meta.themeColor,
 			});
-		});
+		};
 
 		// URL preview endpoint
-		router.get('/url', ctx => this.urlPreviewService.handle(ctx));
-
-		router.get('/api.json', async ctx => {
-			ctx.body = genOpenapiSpec();
-		});
+		fastify.get<{ Querystring: { url: string; lang: string; } }>('/url', (request, reply) => this.urlPreviewService.handle(request, reply));
 
 		const getFeed = async (acct: string) => {
 			const { username, host } = Acct.parse(acct);
@@ -300,45 +296,45 @@ export class ClientServerService {
 		};
 
 		// Atom
-		router.get('/@:user.atom', async ctx => {
-			const feed = await getFeed(ctx.params.user);
+		fastify.get<{ Params: { user: string; } }>('/@:user.atom', async (request, reply) => {
+			const feed = await getFeed(request.params.user);
 
 			if (feed) {
-				ctx.set('Content-Type', 'application/atom+xml; charset=utf-8');
-				ctx.body = feed.atom1();
+				reply.header('Content-Type', 'application/atom+xml; charset=utf-8');
+				return feed.atom1();
 			} else {
-				ctx.status = 404;
+				reply.code(404);
 			}
 		});
 
 		// RSS
-		router.get('/@:user.rss', async ctx => {
-			const feed = await getFeed(ctx.params.user);
+		fastify.get<{ Params: { user: string; } }>('/@:user.rss', async (request, reply) => {
+			const feed = await getFeed(request.params.user);
 
 			if (feed) {
-				ctx.set('Content-Type', 'application/rss+xml; charset=utf-8');
-				ctx.body = feed.rss2();
+				reply.header('Content-Type', 'application/rss+xml; charset=utf-8');
+				return feed.rss2();
 			} else {
-				ctx.status = 404;
+				reply.code(404);
 			}
 		});
 
 		// JSON
-		router.get('/@:user.json', async ctx => {
-			const feed = await getFeed(ctx.params.user);
+		fastify.get<{ Params: { user: string; } }>('/@:user.json', async (request, reply) => {
+			const feed = await getFeed(request.params.user);
 
 			if (feed) {
-				ctx.set('Content-Type', 'application/json; charset=utf-8');
-				ctx.body = feed.json1();
+				reply.header('Content-Type', 'application/json; charset=utf-8');
+				return feed.json1();
 			} else {
-				ctx.status = 404;
+				reply.code(404);
 			}
 		});
 
 		//#region SSR (for crawlers)
 		// User
-		router.get(['/@:user', '/@:user/:sub'], async (ctx, next) => {
-			const { username, host } = Acct.parse(ctx.params.user);
+		fastify.get<{ Params: { user: string; sub?: string; } }>('/@:user/:sub?', async (request, reply) => {
+			const { username, host } = Acct.parse(request.params.user);
 			const user = await this.usersRepository.findOneBy({
 				usernameLower: username.toLowerCase(),
 				host: host ?? IsNull(),
@@ -354,41 +350,41 @@ export class ClientServerService {
 						.map(field => field.value)
 					: [];
 
-				await ctx.render('user', {
+				reply.header('Cache-Control', 'public, max-age=15');
+				return await reply.view('user', {
 					user, profile, me,
 					avatarUrl: await this.userEntityService.getAvatarUrl(user),
-					sub: ctx.params.sub,
+					sub: request.params.sub,
 					instanceName: meta.name ?? 'Misskey',
 					icon: meta.iconUrl,
 					themeColor: meta.themeColor,
 				});
-				ctx.set('Cache-Control', 'public, max-age=15');
 			} else {
 				// リモートユーザーなので
 				// モデレータがAPI経由で参照可能にするために404にはしない
-				await next();
+				return await renderBase(reply);
 			}
 		});
 
-		router.get('/users/:user', async ctx => {
+		fastify.get<{ Params: { user: string; } }>('/users/:user', async (request, reply) => {
 			const user = await this.usersRepository.findOneBy({
-				id: ctx.params.user,
+				id: request.params.user,
 				host: IsNull(),
 				isSuspended: false,
 			});
 
 			if (user == null) {
-				ctx.status = 404;
+				reply.code(404);
 				return;
 			}
 
-			ctx.redirect(`/@${user.username}${ user.host == null ? '' : '@' + user.host}`);
+			reply.redirect(`/@${user.username}${ user.host == null ? '' : '@' + user.host}`);
 		});
 
 		// Note
-		router.get('/notes/:note', async (ctx, next) => {
+		fastify.get<{ Params: { note: string; } }>('/notes/:note', async (request, reply) => {
 			const note = await this.notesRepository.findOneBy({
-				id: ctx.params.note,
+				id: request.params.note,
 				visibility: In(['public', 'home']),
 			});
 
@@ -396,7 +392,8 @@ export class ClientServerService {
 				const _note = await this.noteEntityService.pack(note);
 				const profile = await this.userProfilesRepository.findOneByOrFail({ userId: note.userId });
 				const meta = await this.metaService.fetch();
-				await ctx.render('note', {
+				reply.header('Cache-Control', 'public, max-age=15');
+				return await reply.view('note', {
 					note: _note,
 					profile,
 					avatarUrl: await this.userEntityService.getAvatarUrl(await this.usersRepository.findOneByOrFail({ id: note.userId })),
@@ -406,18 +403,14 @@ export class ClientServerService {
 					icon: meta.iconUrl,
 					themeColor: meta.themeColor,
 				});
-
-				ctx.set('Cache-Control', 'public, max-age=15');
-
-				return;
+			} else {
+				return await renderBase(reply);
 			}
-
-			await next();
 		});
 
 		// Page
-		router.get('/@:user/pages/:page', async (ctx, next) => {
-			const { username, host } = Acct.parse(ctx.params.user);
+		fastify.get<{ Params: { user: string; page: string; } }>('/@:user/pages/:page', async (request, reply) => {
+			const { username, host } = Acct.parse(request.params.user);
 			const user = await this.usersRepository.findOneBy({
 				usernameLower: username.toLowerCase(),
 				host: host ?? IsNull(),
@@ -426,7 +419,7 @@ export class ClientServerService {
 			if (user == null) return;
 
 			const page = await this.pagesRepository.findOneBy({
-				name: ctx.params.page,
+				name: request.params.page,
 				userId: user.id,
 			});
 
@@ -434,7 +427,12 @@ export class ClientServerService {
 				const _page = await this.pageEntityService.pack(page);
 				const profile = await this.userProfilesRepository.findOneByOrFail({ userId: page.userId });
 				const meta = await this.metaService.fetch();
-				await ctx.render('page', {
+				if (['public'].includes(page.visibility)) {
+					reply.header('Cache-Control', 'public, max-age=15');
+				} else {
+					reply.header('Cache-Control', 'private, max-age=0, must-revalidate');
+				}
+				return await reply.view('page', {
 					page: _page,
 					profile,
 					avatarUrl: await this.userEntityService.getAvatarUrl(await this.usersRepository.findOneByOrFail({ id: page.userId })),
@@ -442,31 +440,24 @@ export class ClientServerService {
 					icon: meta.iconUrl,
 					themeColor: meta.themeColor,
 				});
-
-				if (['public'].includes(page.visibility)) {
-					ctx.set('Cache-Control', 'public, max-age=15');
-				} else {
-					ctx.set('Cache-Control', 'private, max-age=0, must-revalidate');
-				}
-
-				return;
+			} else {
+				return await renderBase(reply);
 			}
-
-			await next();
 		});
 
 		// Clip
 		// TODO: 非publicなclipのハンドリング
-		router.get('/clips/:clip', async (ctx, next) => {
+		fastify.get<{ Params: { clip: string; } }>('/clips/:clip', async (request, reply) => {
 			const clip = await this.clipsRepository.findOneBy({
-				id: ctx.params.clip,
+				id: request.params.clip,
 			});
 
 			if (clip) {
 				const _clip = await this.clipEntityService.pack(clip);
 				const profile = await this.userProfilesRepository.findOneByOrFail({ userId: clip.userId });
 				const meta = await this.metaService.fetch();
-				await ctx.render('clip', {
+				reply.header('Cache-Control', 'public, max-age=15');
+				return await reply.view('clip', {
 					clip: _clip,
 					profile,
 					avatarUrl: await this.userEntityService.getAvatarUrl(await this.usersRepository.findOneByOrFail({ id: clip.userId })),
@@ -474,24 +465,21 @@ export class ClientServerService {
 					icon: meta.iconUrl,
 					themeColor: meta.themeColor,
 				});
-
-				ctx.set('Cache-Control', 'public, max-age=15');
-
-				return;
+			} else {
+				return await renderBase(reply);
 			}
-
-			await next();
 		});
 
 		// Gallery post
-		router.get('/gallery/:post', async (ctx, next) => {
-			const post = await this.galleryPostsRepository.findOneBy({ id: ctx.params.post });
+		fastify.get<{ Params: { post: string; } }>('/gallery/:post', async (request, reply) => {
+			const post = await this.galleryPostsRepository.findOneBy({ id: request.params.post });
 
 			if (post) {
 				const _post = await this.galleryPostEntityService.pack(post);
 				const profile = await this.userProfilesRepository.findOneByOrFail({ userId: post.userId });
 				const meta = await this.metaService.fetch();
-				await ctx.render('gallery-post', {
+				reply.header('Cache-Control', 'public, max-age=15');
+				return await reply.view('gallery-post', {
 					post: _post,
 					profile,
 					avatarUrl: await this.userEntityService.getAvatarUrl(await this.usersRepository.findOneByOrFail({ id: post.userId })),
@@ -499,46 +487,39 @@ export class ClientServerService {
 					icon: meta.iconUrl,
 					themeColor: meta.themeColor,
 				});
-
-				ctx.set('Cache-Control', 'public, max-age=15');
-
-				return;
+			} else {
+				return await renderBase(reply);
 			}
-
-			await next();
 		});
 
 		// Channel
-		router.get('/channels/:channel', async (ctx, next) => {
+		fastify.get<{ Params: { channel: string; } }>('/channels/:channel', async (request, reply) => {
 			const channel = await this.channelsRepository.findOneBy({
-				id: ctx.params.channel,
+				id: request.params.channel,
 			});
 
 			if (channel) {
 				const _channel = await this.channelEntityService.pack(channel);
 				const meta = await this.metaService.fetch();
-				await ctx.render('channel', {
+				reply.header('Cache-Control', 'public, max-age=15');
+				return await reply.view('channel', {
 					channel: _channel,
 					instanceName: meta.name ?? 'Misskey',
 					icon: meta.iconUrl,
 					themeColor: meta.themeColor,
 				});
-
-				ctx.set('Cache-Control', 'public, max-age=15');
-
-				return;
+			} else {
+				return await renderBase(reply);
 			}
-
-			await next();
 		});
 		//#endregion
 
-		router.get('/_info_card_', async ctx => {
+		fastify.get('/_info_card_', async (request, reply) => {
 			const meta = await this.metaService.fetch(true);
 
-			ctx.remove('X-Frame-Options');
+			reply.removeHeader('X-Frame-Options');
 
-			await ctx.render('info-card', {
+			return await reply.view('info-card', {
 				version: this.config.version,
 				host: this.config.host,
 				meta: meta,
@@ -547,14 +528,14 @@ export class ClientServerService {
 			});
 		});
 
-		router.get('/bios', async ctx => {
-			await ctx.render('bios', {
+		fastify.get('/bios', async (request, reply) => {
+			return await reply.view('bios', {
 				version: this.config.version,
 			});
 		});
 
-		router.get('/cli', async ctx => {
-			await ctx.render('cli', {
+		fastify.get('/cli', async (request, reply) => {
+			return await reply.view('cli', {
 				version: this.config.version,
 			});
 		});
@@ -562,33 +543,21 @@ export class ClientServerService {
 		const override = (source: string, target: string, depth = 0) =>
 			[, ...target.split('/').filter(x => x), ...source.split('/').filter(x => x).splice(depth)].join('/');
 
-		router.get('/flush', async ctx => {
-			await ctx.render('flush');
+		fastify.get('/flush', async (request, reply) => {
+			return await reply.view('flush');
 		});
 
 		// streamingに非WebSocketリクエストが来た場合にbase htmlをキャシュ付きで返すと、Proxy等でそのパスがキャッシュされておかしくなる
-		router.get('/streaming', async ctx => {
-			ctx.status = 503;
-			ctx.set('Cache-Control', 'private, max-age=0');
+		fastify.get('/streaming', async (request, reply) => {
+			reply.code(503);
+			reply.header('Cache-Control', 'private, max-age=0');
 		});
 
 		// Render base html for all requests
-		router.get('(.*)', async ctx => {
-			const meta = await this.metaService.fetch();
-			await ctx.render('base', {
-				img: meta.bannerUrl,
-				title: meta.name ?? 'Misskey',
-				instanceName: meta.name ?? 'Misskey',
-				desc: meta.description,
-				icon: meta.iconUrl,
-				themeColor: meta.themeColor,
-			});
-			ctx.set('Cache-Control', 'public, max-age=15');
+		fastify.get('*', async (request, reply) => {
+			return await renderBase(reply);
 		});
 
-		// Register router
-		app.use(router.routes());
-
-		return app;
+		done();
 	}
 }
diff --git a/packages/backend/src/server/web/UrlPreviewService.ts b/packages/backend/src/server/web/UrlPreviewService.ts
index f5dddd2db7..69f52cc2f2 100644
--- a/packages/backend/src/server/web/UrlPreviewService.ts
+++ b/packages/backend/src/server/web/UrlPreviewService.ts
@@ -1,5 +1,6 @@
 import { Inject, Injectable } from '@nestjs/common';
 import summaly from 'summaly';
+import { FastifyRequest, FastifyReply } from 'fastify';
 import { DI } from '@/di-symbols.js';
 import type { UsersRepository } from '@/models/index.js';
 import type { Config } from '@/config.js';
@@ -8,7 +9,6 @@ import { HttpRequestService } from '@/core/HttpRequestService.js';
 import type Logger from '@/logger.js';
 import { query } from '@/misc/prelude/url.js';
 import { LoggerService } from '@/core/LoggerService.js';
-import type Koa from 'koa';
 
 @Injectable()
 export class UrlPreviewService {
@@ -39,16 +39,19 @@ export class UrlPreviewService {
 			: null;
 	}
 
-	public async handle(ctx: Koa.Context) {
-		const url = ctx.query.url;
+	public async handle(
+		request: FastifyRequest<{ Querystring: { url: string; lang: string; } }>,
+		reply: FastifyReply,
+	) {
+		const url = request.query.url;
 		if (typeof url !== 'string') {
-			ctx.status = 400;
+			reply.code(400);
 			return;
 		}
 	
-		const lang = ctx.query.lang;
+		const lang = request.query.lang;
 		if (Array.isArray(lang)) {
-			ctx.status = 400;
+			reply.code(400);
 			return;
 		}
 	
@@ -73,14 +76,14 @@ export class UrlPreviewService {
 			summary.thumbnail = this.wrap(summary.thumbnail);
 	
 			// Cache 7days
-			ctx.set('Cache-Control', 'max-age=604800, immutable');
+			reply.header('Cache-Control', 'max-age=604800, immutable');
 	
-			ctx.body = summary;
+			return summary;
 		} catch (err) {
 			this.logger.warn(`Failed to get preview of ${url}: ${err}`);
-			ctx.status = 200;
-			ctx.set('Cache-Control', 'max-age=86400, immutable');
-			ctx.body = '{}';
+			reply.code(200);
+			reply.header('Cache-Control', 'max-age=86400, immutable');
+			return {};
 		}
 	}
 }
diff --git a/packages/backend/src/server/web/bios.js b/packages/backend/src/server/web/bios.js
index d06dee801a..c2ce5c3814 100644
--- a/packages/backend/src/server/web/bios.js
+++ b/packages/backend/src/server/web/bios.js
@@ -10,7 +10,7 @@ window.onload = async () => {
 			if (i) data.i = i;
 	
 			// Send request
-			fetch(endpoint.indexOf('://') > -1 ? endpoint : `/api/${endpoint}`, {
+			window.fetch(endpoint.indexOf('://') > -1 ? endpoint : `/api/${endpoint}`, {
 				method: 'POST',
 				body: JSON.stringify(data),
 				credentials: 'omit',
diff --git a/packages/backend/src/server/web/boot.js b/packages/backend/src/server/web/boot.js
index 2aef689d3f..ffd8b8941c 100644
--- a/packages/backend/src/server/web/boot.js
+++ b/packages/backend/src/server/web/boot.js
@@ -42,7 +42,7 @@
 			}
 		}
 
-		const res = await fetch(`/assets/locales/${lang}.${v}.json`);
+		const res = await window.fetch(`/assets/locales/${lang}.${v}.json`);
 		if (res.status === 200) {
 			localStorage.setItem('lang', lang);
 			localStorage.setItem('locale', await res.text());
@@ -290,9 +290,13 @@
 	// eslint-disable-next-line no-inner-declarations
 	async function checkUpdate() {
 		try {
-			const res = await fetch('/api/meta', {
+			const res = await window.fetch('/api/meta', {
 				method: 'POST',
-				cache: 'no-cache'
+				cache: 'no-cache',
+				body: '{}',
+				headers: {
+					'Content-Type': 'application/json',
+				},
 			});
 
 			const meta = await res.json();