diff --git a/packages/backend/package.json b/packages/backend/package.json
index b584a5691..6f6344102 100644
--- a/packages/backend/package.json
+++ b/packages/backend/package.json
@@ -34,6 +34,7 @@
 		"@koa/cors": "3.4.3",
 		"@koa/multer": "3.0.2",
 		"@koa/router": "9.0.1",
+		"@msgpack/msgpack": "3.0.0-beta2",
 		"@peertube/http-signature": "1.7.0",
 		"@redocly/openapi-core": "1.0.0-beta.120",
 		"@sinonjs/fake-timers": "9.1.2",
@@ -43,7 +44,6 @@
 		"ajv": "8.12.0",
 		"archiver": "5.3.1",
 		"argon2": "^0.30.3",
-		"async-mutex": "^0.4.0",
 		"autobind-decorator": "2.4.0",
 		"autolinker": "4.0.0",
 		"autwh": "0.1.0",
diff --git a/packages/backend/src/misc/cache.ts b/packages/backend/src/misc/cache.ts
index 9abebc91c..d790313d1 100644
--- a/packages/backend/src/misc/cache.ts
+++ b/packages/backend/src/misc/cache.ts
@@ -1,43 +1,75 @@
+import { redisClient } from "@/db/redis.js";
+import { nativeRandomStr } from "native-utils/built/index.js";
+import { encode, decode } from "@msgpack/msgpack";
+import { ChainableCommander } from "ioredis";
+
 export class Cache<T> {
-	public cache: Map<string | null, { date: number; value: T }>;
-	private lifetime: number;
+	private ttl: number;
+	private fingerprint: string;
 
-	constructor(lifetime: Cache<never>["lifetime"]) {
-		this.cache = new Map();
-		this.lifetime = lifetime;
+	constructor(ttl: number) {
+		this.ttl = ttl;
+		this.fingerprint = `cache:${nativeRandomStr(32)}`;
 	}
 
-	public set(key: string | null, value: T): void {
-		this.cache.set(key, {
-			date: Date.now(),
-			value,
-		});
+	private prefixedKey(key: string | null): string {
+		return key ? `${this.fingerprint}:${key}` : this.fingerprint;
 	}
 
-	public get(key: string | null): T | undefined {
-		const cached = this.cache.get(key);
-		if (cached == null) return undefined;
-		if (Date.now() - cached.date > this.lifetime) {
-			this.cache.delete(key);
-			return undefined;
+	public async set(key: string | null, value: T, transaction?: ChainableCommander): Promise<void> {
+		const _key = this.prefixedKey(key);
+		const _value = Buffer.from(encode(value));
+		const commander = transaction ?? redisClient;
+		if (this.ttl === Infinity) {
+			await commander.set(_key, _value);
+		} else {
+			await commander.set(_key, _value, "PX", this.ttl);
 		}
-		return cached.value;
 	}
 
-	public delete(key: string | null) {
-		this.cache.delete(key);
+	public async get(key: string | null): Promise<T | undefined> {
+		const _key = this.prefixedKey(key);
+		const cached = await redisClient.getBuffer(_key);
+		if (cached === null) return undefined;
+
+		return decode(cached) as T;
+	}
+
+	public async getAll(): Promise<Map<string, T>> {
+		const keys = await redisClient.keys(`${this.fingerprint}*`);
+		const map = new Map<string, T>();
+		if (keys.length === 0) {
+			return map;
+		}
+		const values = await redisClient.mgetBuffer(keys);
+
+		for (const [i, key] of keys.entries()) {
+			const val = values[i];
+			if (val !== null) {
+				map.set(key, decode(val) as T);
+			}
+		}
+
+		return map;
+	}
+
+	public async delete(...keys: (string | null)[]): Promise<void> {
+		if (keys.length > 0) {
+			const _keys = keys.map(this.prefixedKey);
+			await redisClient.del(_keys);
+		}
 	}
 
 	/**
-	 * キャッシュがあればそれを返し、無ければfetcherを呼び出して結果をキャッシュ&返します
-	 * optional: キャッシュが存在してもvalidatorでfalseを返すとキャッシュ無効扱いにします
+	 * Returns if cached value exists. Otherwise, calls fetcher and caches.
+	 * Overwrites cached value if invalidated by the optional validator.
 	 */
 	public async fetch(
 		key: string | null,
 		fetcher: () => Promise<T>,
 		validator?: (cachedValue: T) => boolean,
 	): Promise<T> {
-		const cachedValue = this.get(key);
+		const cachedValue = await this.get(key);
 		if (cachedValue !== undefined) {
 			if (validator) {
 				if (validator(cachedValue)) {
@@ -52,20 +84,20 @@ export class Cache<T> {
 
 		// Cache MISS
 		const value = await fetcher();
-		this.set(key, value);
+		await this.set(key, value);
 		return value;
 	}
 
 	/**
-	 * キャッシュがあればそれを返し、無ければfetcherを呼び出して結果をキャッシュ&返します
-	 * optional: キャッシュが存在してもvalidatorでfalseを返すとキャッシュ無効扱いにします
+	 * Returns if cached value exists. Otherwise, calls fetcher and caches if the fetcher returns a value.
+	 * Overwrites cached value if invalidated by the optional validator.
 	 */
 	public async fetchMaybe(
 		key: string | null,
 		fetcher: () => Promise<T | undefined>,
 		validator?: (cachedValue: T) => boolean,
 	): Promise<T | undefined> {
-		const cachedValue = this.get(key);
+		const cachedValue = await this.get(key);
 		if (cachedValue !== undefined) {
 			if (validator) {
 				if (validator(cachedValue)) {
@@ -81,7 +113,7 @@ export class Cache<T> {
 		// Cache MISS
 		const value = await fetcher();
 		if (value !== undefined) {
-			this.set(key, value);
+			await this.set(key, value);
 		}
 		return value;
 	}
diff --git a/packages/backend/src/misc/emoji-meta.ts b/packages/backend/src/misc/emoji-meta.ts
index fd9d9baa5..45364bdcb 100644
--- a/packages/backend/src/misc/emoji-meta.ts
+++ b/packages/backend/src/misc/emoji-meta.ts
@@ -1,9 +1,10 @@
 import probeImageSize from "probe-image-size";
-import { Mutex, withTimeout } from "async-mutex";
+import { Mutex } from "redis-semaphore";
 
 import { FILE_TYPE_BROWSERSAFE } from "@/const.js";
 import Logger from "@/services/logger.js";
 import { Cache } from "./cache.js";
+import { redisClient } from "@/db/redis.js";
 
 export type Size = {
 	width: number;
@@ -11,23 +12,30 @@ export type Size = {
 };
 
 const cache = new Cache<boolean>(1000 * 60 * 10); // once every 10 minutes for the same url
-const mutex = withTimeout(new Mutex(), 1000);
+const logger = new Logger("emoji");
 
 export async function getEmojiSize(url: string): Promise<Size> {
-	const logger = new Logger("emoji");
+	let attempted = true;
 
-	await mutex.runExclusive(() => {
-		const attempted = cache.get(url);
-		if (!attempted) {
-			cache.set(url, true);
-		} else {
-			logger.warn(`Attempt limit exceeded: ${url}`);
-			throw new Error("Too many attempts");
-		}
-	});
+	const lock = new Mutex(redisClient, "getEmojiSize");
+	await lock.acquire();
 
 	try {
-		logger.info(`Retrieving emoji size from ${url}`);
+		attempted = (await cache.get(url)) === true;
+		if (!attempted) {
+			await cache.set(url, true);
+		}
+	} finally {
+		await lock.release();
+	}
+
+	if (attempted) {
+		logger.warn(`Attempt limit exceeded: ${url}`);
+		throw new Error("Too many attempts");
+	}
+
+	try {
+		logger.debug(`Retrieving emoji size from ${url}`);
 		const { width, height, mime } = await probeImageSize(url, {
 			timeout: 5000,
 		});
diff --git a/packages/backend/src/misc/populate-emojis.ts b/packages/backend/src/misc/populate-emojis.ts
index 7aee4ec25..ce25dd559 100644
--- a/packages/backend/src/misc/populate-emojis.ts
+++ b/packages/backend/src/misc/populate-emojis.ts
@@ -7,6 +7,7 @@ import { isSelfHost, toPunyNullable } from "./convert-host.js";
 import { decodeReaction } from "./reaction-lib.js";
 import config from "@/config/index.js";
 import { query } from "@/prelude/url.js";
+import { redisClient } from "@/db/redis.js";
 
 const cache = new Cache<Emoji | null>(1000 * 60 * 60 * 12);
 
@@ -75,7 +76,7 @@ export async function populateEmoji(
 
 	if (emoji && !(emoji.width && emoji.height)) {
 		emoji = await queryOrNull();
-		cache.set(cacheKey, emoji);
+		await cache.set(cacheKey, emoji);
 	}
 
 	if (emoji == null) return null;
@@ -150,7 +151,7 @@ export async function prefetchEmojis(
 	emojis: { name: string; host: string | null }[],
 ): Promise<void> {
 	const notCachedEmojis = emojis.filter(
-		(emoji) => cache.get(`${emoji.name} ${emoji.host}`) == null,
+		async (emoji) => !(await cache.get(`${emoji.name} ${emoji.host}`)),
 	);
 	const emojisQuery: any[] = [];
 	const hosts = new Set(notCachedEmojis.map((e) => e.host));
@@ -169,7 +170,9 @@ export async function prefetchEmojis(
 					select: ["name", "host", "originalUrl", "publicUrl"],
 			  })
 			: [];
+	const trans = redisClient.multi();
 	for (const emoji of _emojis) {
-		cache.set(`${emoji.name} ${emoji.host}`, emoji);
+		cache.set(`${emoji.name} ${emoji.host}`, emoji, trans);
 	}
+	await trans.exec();
 }
diff --git a/packages/backend/src/remote/activitypub/models/person.ts b/packages/backend/src/remote/activitypub/models/person.ts
index f8208e6d7..c541e9ae5 100644
--- a/packages/backend/src/remote/activitypub/models/person.ts
+++ b/packages/backend/src/remote/activitypub/models/person.ts
@@ -135,14 +135,14 @@ export async function fetchPerson(
 ): Promise<CacheableUser | null> {
 	if (typeof uri !== "string") throw new Error("uri is not string");
 
-	const cached = uriPersonCache.get(uri);
+	const cached = await uriPersonCache.get(uri);
 	if (cached) return cached;
 
 	// Fetch from the database if the URI points to this server
 	if (uri.startsWith(`${config.url}/`)) {
 		const id = uri.split("/").pop();
 		const u = await Users.findOneBy({ id });
-		if (u) uriPersonCache.set(uri, u);
+		if (u) await uriPersonCache.set(uri, u);
 		return u;
 	}
 
@@ -150,7 +150,7 @@ export async function fetchPerson(
 	const exist = await Users.findOneBy({ uri });
 
 	if (exist) {
-		uriPersonCache.set(uri, exist);
+		await uriPersonCache.set(uri, exist);
 		return exist;
 	}
 	//#endregion
diff --git a/packages/backend/src/services/chart/charts/active-users.ts b/packages/backend/src/services/chart/charts/active-users.ts
index 7a0c45cfa..15317e68b 100644
--- a/packages/backend/src/services/chart/charts/active-users.ts
+++ b/packages/backend/src/services/chart/charts/active-users.ts
@@ -25,12 +25,12 @@ export default class ActiveUsersChart extends Chart<typeof schema> {
 		return {};
 	}
 
-	public async read(user: {
+	public read(user: {
 		id: User["id"];
 		host: null;
 		createdAt: User["createdAt"];
-	}): Promise<void> {
-		await this.commit({
+	})  {
+		this.commit({
 			read: [user.id],
 			registeredWithinWeek:
 				Date.now() - user.createdAt.getTime() < week ? [user.id] : [],
diff --git a/packages/backend/src/services/instance-actor.ts b/packages/backend/src/services/instance-actor.ts
index 50ce227eb..9240f3107 100644
--- a/packages/backend/src/services/instance-actor.ts
+++ b/packages/backend/src/services/instance-actor.ts
@@ -9,7 +9,7 @@ const ACTOR_USERNAME = "instance.actor" as const;
 const cache = new Cache<ILocalUser>(Infinity);
 
 export async function getInstanceActor(): Promise<ILocalUser> {
-	const cached = cache.get(null);
+	const cached = await cache.get(null);
 	if (cached) return cached;
 
 	const user = (await Users.findOneBy({
@@ -18,11 +18,11 @@ export async function getInstanceActor(): Promise<ILocalUser> {
 	})) as ILocalUser | undefined;
 
 	if (user) {
-		cache.set(null, user);
+		await cache.set(null, user);
 		return user;
 	} else {
 		const created = (await createSystemUser(ACTOR_USERNAME)) as ILocalUser;
-		cache.set(null, created);
+		await cache.set(null, created);
 		return created;
 	}
 }
diff --git a/packages/backend/src/services/register-or-fetch-instance-doc.ts b/packages/backend/src/services/register-or-fetch-instance-doc.ts
index 4c3570e90..ddb9ce241 100644
--- a/packages/backend/src/services/register-or-fetch-instance-doc.ts
+++ b/packages/backend/src/services/register-or-fetch-instance-doc.ts
@@ -9,25 +9,25 @@ const cache = new Cache<Instance>(1000 * 60 * 60);
 export async function registerOrFetchInstanceDoc(
 	host: string,
 ): Promise<Instance> {
-	host = toPuny(host);
+	const _host = toPuny(host);
 
-	const cached = cache.get(host);
+	const cached = await cache.get(_host);
 	if (cached) return cached;
 
-	const index = await Instances.findOneBy({ host });
+	const index = await Instances.findOneBy({ host: _host });
 
 	if (index == null) {
 		const i = await Instances.insert({
 			id: genId(),
-			host,
+			host: _host,
 			caughtAt: new Date(),
 			lastCommunicatedAt: new Date(),
 		}).then((x) => Instances.findOneByOrFail(x.identifiers[0]));
 
-		cache.set(host, i);
+		await cache.set(_host, i);
 		return i;
 	} else {
-		cache.set(host, index);
+		await cache.set(_host, index);
 		return index;
 	}
 }
diff --git a/packages/backend/src/services/relay.ts b/packages/backend/src/services/relay.ts
index bec4b1f86..2325f76c6 100644
--- a/packages/backend/src/services/relay.ts
+++ b/packages/backend/src/services/relay.ts
@@ -90,7 +90,7 @@ async function updateRelaysCache() {
 	const relays = await Relays.findBy({
 		status: "accepted",
 	});
-	relaysCache.set(null, relays);
+	await relaysCache.set(null, relays);
 }
 
 export async function relayRejected(id: string) {
diff --git a/packages/backend/src/services/user-cache.ts b/packages/backend/src/services/user-cache.ts
index 949244855..373fb8686 100644
--- a/packages/backend/src/services/user-cache.ts
+++ b/packages/backend/src/services/user-cache.ts
@@ -6,7 +6,7 @@ import type {
 import { User } from "@/models/entities/user.js";
 import { Users } from "@/models/index.js";
 import { Cache } from "@/misc/cache.js";
-import { subscriber } from "@/db/redis.js";
+import { redisClient, subscriber } from "@/db/redis.js";
 
 export const userByIdCache = new Cache<CacheableUser>(Infinity);
 export const localUserByNativeTokenCache = new Cache<CacheableLocalUser | null>(
@@ -22,13 +22,12 @@ subscriber.on("message", async (_, data) => {
 		const { type, body } = obj.message;
 		switch (type) {
 			case "localUserUpdated": {
-				userByIdCache.delete(body.id);
-				localUserByIdCache.delete(body.id);
-				localUserByNativeTokenCache.cache.forEach((v, k) => {
-					if (v.value?.id === body.id) {
-						localUserByNativeTokenCache.delete(k);
-					}
-				});
+				await userByIdCache.delete(body.id);
+				await localUserByIdCache.delete(body.id);
+				const toDelete = Array.from(await localUserByNativeTokenCache.getAll())
+					.filter((v) => v[1]?.id === body.id)
+					.map((v) => v[0]);
+				await localUserByNativeTokenCache.delete(...toDelete);
 				break;
 			}
 			case "userChangeSuspendedState":
@@ -36,15 +35,17 @@ subscriber.on("message", async (_, data) => {
 			case "userChangeModeratorState":
 			case "remoteUserUpdated": {
 				const user = await Users.findOneByOrFail({ id: body.id });
-				userByIdCache.set(user.id, user);
-				for (const [k, v] of uriPersonCache.cache.entries()) {
-					if (v.value?.id === user.id) {
-						uriPersonCache.set(k, user);
+				await userByIdCache.set(user.id, user);
+				const trans = redisClient.multi();
+				for (const [k, v] of (await uriPersonCache.getAll()).entries()) {
+					if (v?.id === user.id) {
+						await uriPersonCache.set(k, user, trans);
 					}
 				}
+				await trans.exec();
 				if (Users.isLocalUser(user)) {
-					localUserByNativeTokenCache.set(user.token, user);
-					localUserByIdCache.set(user.id, user);
+					await localUserByNativeTokenCache.set(user.token, user);
+					await localUserByIdCache.set(user.id, user);
 				}
 				break;
 			}
@@ -52,8 +53,8 @@ subscriber.on("message", async (_, data) => {
 				const user = (await Users.findOneByOrFail({
 					id: body.id,
 				})) as ILocalUser;
-				localUserByNativeTokenCache.delete(body.oldToken);
-				localUserByNativeTokenCache.set(body.newToken, user);
+				await localUserByNativeTokenCache.delete(body.oldToken);
+				await localUserByNativeTokenCache.set(body.newToken, user);
 				break;
 			}
 			default:
diff --git a/pnpm-lock.yaml b/pnpm-lock.yaml
index 1002a6f95..560bb55a3 100644
--- a/pnpm-lock.yaml
+++ b/pnpm-lock.yaml
@@ -105,6 +105,9 @@ importers:
       '@koa/router':
         specifier: 9.0.1
         version: 9.0.1
+      '@msgpack/msgpack':
+        specifier: 3.0.0-beta2
+        version: 3.0.0-beta2
       '@peertube/http-signature':
         specifier: 1.7.0
         version: 1.7.0
@@ -132,9 +135,6 @@ importers:
       argon2:
         specifier: ^0.30.3
         version: 0.30.3
-      async-mutex:
-        specifier: ^0.4.0
-        version: 0.4.0
       autobind-decorator:
         specifier: 2.4.0
         version: 2.4.0
@@ -786,7 +786,7 @@ importers:
         version: 2.30.0
       emojilib:
         specifier: github:thatonecalculator/emojilib
-        version: github.com/thatonecalculator/emojilib/542fcc1a25003afad78f3248ceee8ac6980ddeb8
+        version: github.com/thatonecalculator/emojilib/06944984a61ee799b7083894258f5fa318d932d1
       escape-regexp:
         specifier: 0.0.1
         version: 0.0.1
@@ -2277,6 +2277,11 @@ packages:
       os-filter-obj: 2.0.0
     dev: true
 
+  /@msgpack/msgpack@3.0.0-beta2:
+    resolution: {integrity: sha512-y+l1PNV0XDyY8sM3YtuMLK5vE3/hkfId+Do8pLo/OPxfxuFAUwcGz3oiiUuV46/aBpwTzZ+mRWVMtlSKbradhw==}
+    engines: {node: '>= 14'}
+    dev: false
+
   /@msgpackr-extract/msgpackr-extract-darwin-arm64@3.0.2:
     resolution: {integrity: sha512-9bfjwDxIDWmmOKusUcqdS4Rw+SETlp9Dy39Xui9BEGEk19dDwH0jhipwFzEff/pFg95NKymc6TOTbRKcWeRqyQ==}
     cpu: [arm64]
@@ -4496,12 +4501,6 @@ packages:
       stream-exhaust: 1.0.2
     dev: true
 
-  /async-mutex@0.4.0:
-    resolution: {integrity: sha512-eJFZ1YhRR8UN8eBLoNzcDPcy/jqjsg6I1AP+KvWQX80BqOSW1oJPJXDylPUEeMr2ZQvHgnQ//Lp6f3RQ1zI7HA==}
-    dependencies:
-      tslib: 2.6.0
-    dev: false
-
   /async-settle@1.0.0:
     resolution: {integrity: sha512-VPXfB4Vk49z1LHHodrEQ6Xf7W4gg1w0dAPROHngx7qgDjqmIQ+fXmwgGXTW/ITLai0YLSvWepJOP9EVpMnEAcw==}
     engines: {node: '>= 0.10'}
@@ -15772,8 +15771,8 @@ packages:
       url-polyfill: 1.1.12
     dev: true
 
-  github.com/thatonecalculator/emojilib/542fcc1a25003afad78f3248ceee8ac6980ddeb8:
-    resolution: {tarball: https://codeload.github.com/thatonecalculator/emojilib/tar.gz/542fcc1a25003afad78f3248ceee8ac6980ddeb8}
+  github.com/thatonecalculator/emojilib/06944984a61ee799b7083894258f5fa318d932d1:
+    resolution: {tarball: https://codeload.github.com/thatonecalculator/emojilib/tar.gz/06944984a61ee799b7083894258f5fa318d932d1}
     name: emojilib
     version: 3.0.10
     dev: true