diff --git a/.config/example.yml b/.config/example.yml
index f73f4f1d79..12665bcb38 100644
--- a/.config/example.yml
+++ b/.config/example.yml
@@ -67,7 +67,7 @@ redis:
   #db: 1
   #user: default
 
-#   ┌─────────────────────────────┐
+#   ┌────────────────────────────┐
 #───┘ Cache server configuration └─────────────────────────────────────
 
 # A Redis-compatible server (DragonflyDB, Keydb, Redis) for caching
@@ -81,6 +81,14 @@ redis:
   #prefix: example-prefix
   #db: 1
 
+#   ┌────────────────────────┐
+#───┘ ScyllaDB configuration └─────────────────────────────────────
+
+# scylla:
+#   nodes: ['localhost:9042']
+#   keyspace: calckey
+#   replicationFactor: 1
+
 # Please configure either MeiliSearch *or* Sonic.
 # If both MeiliSearch and Sonic configurations are present, MeiliSearch will take precedence.
 
diff --git a/packages/backend/package.json b/packages/backend/package.json
index cedd9bee71..cc94f8ee24 100644
--- a/packages/backend/package.json
+++ b/packages/backend/package.json
@@ -53,6 +53,7 @@
 		"bull": "4.10.4",
 		"cacheable-lookup": "7.0.0",
 		"calckey-js": "workspace:*",
+		"cassandra-driver": "^4.6.4",
 		"cbor": "8.1.0",
 		"chalk": "5.3.0",
 		"chalk-template": "0.4.0",
diff --git a/packages/backend/src/config/types.ts b/packages/backend/src/config/types.ts
index 7789c26e07..49a96642f2 100644
--- a/packages/backend/src/config/types.ts
+++ b/packages/backend/src/config/types.ts
@@ -16,6 +16,11 @@ export type Source = {
 		disableCache?: boolean;
 		extra?: { [x: string]: string };
 	};
+	scylla?: {
+		nodes: string[];
+		keyspace: string;
+		replicationFactor: number;
+	},
 	redis: {
 		host: string;
 		port: number;
diff --git a/packages/backend/src/db/scylla.ts b/packages/backend/src/db/scylla.ts
new file mode 100644
index 0000000000..443f23793b
--- /dev/null
+++ b/packages/backend/src/db/scylla.ts
@@ -0,0 +1,28 @@
+import config from "@/config/index.js";
+import { Client } from "cassandra-driver";
+
+function newClient(): Client | null {
+	if (!config.scylla) {
+		return null;
+	}
+
+	return new Client({
+		contactPoints: config.scylla.nodes,
+		keyspace: config.scylla.keyspace,
+	});
+}
+
+export const scyllaClient = newClient();
+
+export const prepared = {
+	timeline: {
+		insert: "",
+		select: "",
+		delete: "",
+	},
+	notification: {
+		insert: "",
+		select: "",
+		delete: "",
+	}
+}
diff --git a/packages/backend/src/models/repositories/user.ts b/packages/backend/src/models/repositories/user.ts
index e4aab896d0..7c3f418e50 100644
--- a/packages/backend/src/models/repositories/user.ts
+++ b/packages/backend/src/models/repositories/user.ts
@@ -38,6 +38,7 @@ import {
 	UserSecurityKeys,
 } from "../index.js";
 import type { Instance } from "../entities/instance.js";
+import { userByIdCache } from "@/services/user-cache.js";
 
 const userInstanceCache = new Cache<Instance | null>(
 	"userInstance",
@@ -382,23 +383,24 @@ export const UserRepository = db.getRepository(User).extend({
 			options,
 		);
 
-		let user: User;
+		let id: string;
 
 		if (typeof src === "object") {
-			user = src;
-			if (src.avatar === undefined && src.avatarId)
-				src.avatar = (await DriveFiles.findOneBy({ id: src.avatarId })) ?? null;
-			if (src.banner === undefined && src.bannerId)
-				src.banner = (await DriveFiles.findOneBy({ id: src.bannerId })) ?? null;
+			id = src.id;
 		} else {
-			user = await this.findOneOrFail({
-				where: { id: src },
+			id = src;
+		}
+
+		const user = await userByIdCache.fetch(id, () =>
+			this.findOneOrFail({
+				where: { id },
 				relations: {
 					avatar: true,
 					banner: true,
 				},
-			});
-		}
+			}),
+			true,
+		);
 
 		const meId = me ? me.id : null;
 		const isMe = meId === user.id;
diff --git a/packages/backend/src/remote/activitypub/db-resolver.ts b/packages/backend/src/remote/activitypub/db-resolver.ts
index a710b9f115..cbd8b4312c 100644
--- a/packages/backend/src/remote/activitypub/db-resolver.ts
+++ b/packages/backend/src/remote/activitypub/db-resolver.ts
@@ -128,8 +128,12 @@ export default class DbResolver {
 				(await userByIdCache.fetchMaybe(
 					parsed.id,
 					() =>
-						Users.findOneBy({
-							id: parsed.id,
+						Users.findOne({
+							where: { id: parsed.id },
+							relations: {
+								avatar: true,
+								banner: true,
+							},
 						}).then((x) => x ?? undefined),
 					true,
 				)) ?? null
@@ -173,7 +177,11 @@ export default class DbResolver {
 		return {
 			user: (await userByIdCache.fetch(
 				key.userId,
-				() => Users.findOneByOrFail({ id: key.userId }),
+				() =>
+					Users.findOneOrFail({
+						where: { id: key.userId },
+						relations: { avatar: true, banner: true },
+					}),
 				true,
 			)) as CacheableRemoteUser,
 			key,
diff --git a/packages/backend/src/server/api/endpoints/i/update.ts b/packages/backend/src/server/api/endpoints/i/update.ts
index 0637251a6b..273ac422a7 100644
--- a/packages/backend/src/server/api/endpoints/i/update.ts
+++ b/packages/backend/src/server/api/endpoints/i/update.ts
@@ -14,6 +14,8 @@ import { normalizeForSearch } from "@/misc/normalize-for-search.js";
 import { langmap } from "@/misc/langmap.js";
 import { ApiError } from "../../error.js";
 import define from "../../define.js";
+import { userByIdCache } from "@/services/user-cache.js";
+import type { DriveFile } from "@/models/entities/drive-file.js";
 
 export const meta = {
 	tags: ["account"],
@@ -204,8 +206,9 @@ export default define(meta, paramDef, async (ps, _user, token) => {
 	if (ps.emailNotificationTypes !== undefined)
 		profileUpdates.emailNotificationTypes = ps.emailNotificationTypes;
 
+	let avatar: DriveFile | null = null;
 	if (ps.avatarId) {
-		const avatar = await DriveFiles.findOneBy({ id: ps.avatarId });
+		avatar = await DriveFiles.findOneBy({ id: ps.avatarId });
 
 		if (avatar == null || avatar.userId !== user.id)
 			throw new ApiError(meta.errors.noSuchAvatar);
@@ -213,8 +216,9 @@ export default define(meta, paramDef, async (ps, _user, token) => {
 			throw new ApiError(meta.errors.avatarNotAnImage);
 	}
 
+	let banner: DriveFile | null = null;
 	if (ps.bannerId) {
-		const banner = await DriveFiles.findOneBy({ id: ps.bannerId });
+		banner = await DriveFiles.findOneBy({ id: ps.bannerId });
 
 		if (banner == null || banner.userId !== user.id)
 			throw new ApiError(meta.errors.noSuchBanner);
@@ -278,7 +282,10 @@ export default define(meta, paramDef, async (ps, _user, token) => {
 	updateUsertags(user, tags);
 	//#endregion
 
-	if (Object.keys(updates).length > 0) await Users.update(user.id, updates);
+	if (Object.keys(updates).length > 0) {
+		await Users.update(user.id, updates);
+		await userByIdCache.set(user.id, { ...user, ...updates, avatar, banner });
+	}
 	if (Object.keys(profileUpdates).length > 0)
 		await UserProfiles.update(user.id, profileUpdates);
 
diff --git a/packages/backend/src/server/api/endpoints/notes/local-timeline.ts b/packages/backend/src/server/api/endpoints/notes/local-timeline.ts
index 82e93e371f..7967dbaec1 100644
--- a/packages/backend/src/server/api/endpoints/notes/local-timeline.ts
+++ b/packages/backend/src/server/api/endpoints/notes/local-timeline.ts
@@ -89,17 +89,10 @@ export default define(meta, paramDef, async (ps, user) => {
 		ps.untilDate,
 	)
 		.andWhere("(note.visibility = 'public') AND (note.userHost IS NULL)")
-		.innerJoinAndSelect("note.user", "user")
-		.leftJoinAndSelect("user.avatar", "avatar")
-		.leftJoinAndSelect("user.banner", "banner")
 		.leftJoinAndSelect("note.reply", "reply")
 		.leftJoinAndSelect("note.renote", "renote")
-		.leftJoinAndSelect("reply.user", "replyUser")
-		.leftJoinAndSelect("replyUser.avatar", "replyUserAvatar")
-		.leftJoinAndSelect("replyUser.banner", "replyUserBanner")
-		.leftJoinAndSelect("renote.user", "renoteUser")
-		.leftJoinAndSelect("renoteUser.avatar", "renoteUserAvatar")
-		.leftJoinAndSelect("renoteUser.banner", "renoteUserBanner");
+
+	// TODO: Use materialized view of postgres as much for non-denormalizable columns as possible.
 
 	generateChannelQuery(query, user);
 	generateRepliesQuery(query, ps.withReplies, user);
diff --git a/packages/backend/src/server/api/endpoints/notes/timeline.ts b/packages/backend/src/server/api/endpoints/notes/timeline.ts
index d629deebb6..606e83ad1f 100644
--- a/packages/backend/src/server/api/endpoints/notes/timeline.ts
+++ b/packages/backend/src/server/api/endpoints/notes/timeline.ts
@@ -92,16 +92,10 @@ export default define(meta, paramDef, async (ps, user) => {
 			}),
 		)
 		.innerJoinAndSelect("note.user", "user")
-		.leftJoinAndSelect("user.avatar", "avatar")
-		.leftJoinAndSelect("user.banner", "banner")
 		.leftJoinAndSelect("note.reply", "reply")
 		.leftJoinAndSelect("note.renote", "renote")
 		.leftJoinAndSelect("reply.user", "replyUser")
-		.leftJoinAndSelect("replyUser.avatar", "replyUserAvatar")
-		.leftJoinAndSelect("replyUser.banner", "replyUserBanner")
 		.leftJoinAndSelect("renote.user", "renoteUser")
-		.leftJoinAndSelect("renoteUser.avatar", "renoteUserAvatar")
-		.leftJoinAndSelect("renoteUser.banner", "renoteUserBanner")
 		.setParameters(followingQuery.getParameters());
 
 	generateChannelQuery(query, user);
diff --git a/packages/backend/src/services/user-cache.ts b/packages/backend/src/services/user-cache.ts
index ed700185df..790fd648f2 100644
--- a/packages/backend/src/services/user-cache.ts
+++ b/packages/backend/src/services/user-cache.ts
@@ -40,7 +40,10 @@ subscriber.on("message", async (_, data) => {
 			case "userChangeSilencedState":
 			case "userChangeModeratorState":
 			case "remoteUserUpdated": {
-				const user = await Users.findOneByOrFail({ id: body.id });
+				const user = await Users.findOneOrFail({
+					where: { id: body.id },
+					relations: { avatar: true, banner: true },
+				});
 				await userByIdCache.set(user.id, user);
 				const trans = redisClient.multi();
 				for (const [k, v] of (await uriPersonCache.getAll()).entries()) {
diff --git a/pnpm-lock.yaml b/pnpm-lock.yaml
index 3ad273c464..b0dabbab5e 100644
--- a/pnpm-lock.yaml
+++ b/pnpm-lock.yaml
@@ -159,6 +159,9 @@ importers:
       calckey-js:
         specifier: workspace:*
         version: link:../calckey-js
+      cassandra-driver:
+        specifier: ^4.6.4
+        version: 4.6.4
       cbor:
         specifier: 8.1.0
         version: 8.1.0
@@ -6220,6 +6223,16 @@ packages:
   /caseless@0.12.0:
     resolution: {integrity: sha512-4tYFyifaFfGacoiObjJegolkwSU4xQNGbVgUiNYVUxbQ2x2lUsFvY4hVgVzGiIe6WLOPqycWXA40l+PWsxthUw==}
 
+  /cassandra-driver@4.6.4:
+    resolution: {integrity: sha512-SksbIK0cZ2QZRx8ti7w+PnLqldyY+6kU2gRWFChwXFTtrD/ce8cQICDEHxyPwx+DeILwRnMrPf9cjUGizYw9Vg==}
+    engines: {node: '>=8'}
+    dependencies:
+      '@types/long': 4.0.2
+      '@types/node': 20.4.1
+      adm-zip: 0.5.10
+      long: 2.4.0
+    dev: false
+
   /cbor@8.1.0:
     resolution: {integrity: sha512-DwGjNW9omn6EwP70aXsn7FQJx5kO12tX0bZkaTjzdVFM6/7nhA4t0EENocKGx6D2Bch9PE2KzCUf5SceBdeijg==}
     engines: {node: '>=12.19'}
@@ -12887,6 +12900,11 @@ packages:
       wrap-ansi: 6.2.0
     dev: true
 
+  /long@2.4.0:
+    resolution: {integrity: sha512-ijUtjmO/n2A5PaosNG9ZGDsQ3vxJg7ZW8vsY8Kp0f2yIZWhSJvjmegV7t+9RPQKxKrvj8yKGehhS+po14hPLGQ==}
+    engines: {node: '>=0.6'}
+    dev: false
+
   /long@4.0.0:
     resolution: {integrity: sha512-XsP+KhQif4bjX1kbuSiySJFNAehNxgLb6hPRGJ9QsUr8ajHkuXGdrHmFUTUUXhDwVX2R5bY4JNZEwbUiMhV+MA==}
     dev: false