diff --git a/packages/backend/src/misc/fetch-meta.ts b/packages/backend/src/misc/fetch-meta.ts
index 4fb69f923..3d66f2d63 100644
--- a/packages/backend/src/misc/fetch-meta.ts
+++ b/packages/backend/src/misc/fetch-meta.ts
@@ -1,6 +1,7 @@
 import { db } from "@/db/postgre.js";
 import { Meta } from "@/models/entities/meta.js";
 import push from 'web-push';
+import { Metas } from "@/models/index.js";
 
 let cache: Meta;
 
@@ -33,41 +34,31 @@ export function metaToPugArgs(meta: Meta): object {
 export async function fetchMeta(noCache = false): Promise<Meta> {
 	if (!noCache && cache) return cache;
 
-	return await db.transaction(async (transactionalEntityManager) => {
-		// New IDs are prioritized because multiple records may have been created due to past bugs.
-		const metas = await transactionalEntityManager.find(Meta, {
-			order: {
-				id: "DESC",
-			},
-		});
-
-		const meta = metas[0];
-
-		if (meta) {
-			cache = meta;
-			return meta;
-		} else {
-			const { publicKey, privateKey } = push.generateVAPIDKeys();
-
-			// If fetchMeta is called at the same time when meta is empty, this part may be called at the same time, so use fail-safe upsert.
-			const saved = await transactionalEntityManager
-				.upsert(
-					Meta,
-					{
-						id: "x",
-						swPublicKey: publicKey,
-						swPrivateKey: privateKey,
-					},
-					["id"],
-				)
-				.then((x) =>
-					transactionalEntityManager.findOneByOrFail(Meta, x.identifiers[0]),
-				);
-
-			cache = saved;
-			return saved;
-		}
+	// New IDs are prioritized because multiple records may have been created due to past bugs.
+	const meta = await Metas.findOne({
+		where: {},
+		order: {
+			id: "DESC",
+		},
 	});
+
+	if (meta) {
+		cache = meta;
+		return meta;
+	}
+
+	const { publicKey, privateKey } = push.generateVAPIDKeys();
+	const data = {
+		id: "x",
+		swPublicKey: publicKey,
+		swPrivateKey: privateKey,
+	};
+
+	// If fetchMeta is called at the same time when meta is empty, this part may be called at the same time, so use fail-safe upsert.
+	await Metas.upsert(data, ["id"]);
+
+	cache = await Metas.findOneByOrFail({ id: data.id });
+	return cache;
 }
 
 setInterval(() => {
diff --git a/packages/backend/src/remote/activitypub/models/person.ts b/packages/backend/src/remote/activitypub/models/person.ts
index e474e1f54..0812f7e7d 100644
--- a/packages/backend/src/remote/activitypub/models/person.ts
+++ b/packages/backend/src/remote/activitypub/models/person.ts
@@ -294,80 +294,77 @@ export async function createPerson(
 		}
 	}
 
-	// Create user
-	let user: IRemoteUser;
+	// Prepare objects
+	let user = new User({
+		id: genId(),
+		avatarId: null,
+		bannerId: null,
+		createdAt: new Date(),
+		lastFetchedAt: new Date(),
+		name: truncate(person.name, nameLength),
+		isLocked: !!person.manuallyApprovesFollowers,
+		movedToUri: person.movedTo,
+		alsoKnownAs: person.alsoKnownAs,
+		isExplorable: !!person.discoverable,
+		username: person.preferredUsername,
+		usernameLower: person.preferredUsername!.toLowerCase(),
+		host,
+		inbox: person.inbox,
+		sharedInbox:
+			person.sharedInbox ||
+			(person.endpoints ? person.endpoints.sharedInbox : undefined),
+		followersUri: person.followers
+			? getApId(person.followers)
+			: undefined,
+		followersCount:
+			followersCount !== undefined
+				? followersCount
+				: person.followers &&
+				typeof person.followers !== "string" &&
+				isCollectionOrOrderedCollection(person.followers)
+					? person.followers.totalItems
+					: undefined,
+		followingCount:
+			followingCount !== undefined
+				? followingCount
+				: person.following &&
+				typeof person.following !== "string" &&
+				isCollectionOrOrderedCollection(person.following)
+					? person.following.totalItems
+					: undefined,
+		featured: person.featured ? getApId(person.featured) : undefined,
+		uri: person.id,
+		tags,
+		isBot,
+		isCat: (person as any).isCat === true,
+	}) as IRemoteUser;
+
+	const profile = new UserProfile({
+		userId: user.id,
+		description: person.summary
+			? await htmlToMfm(truncate(person.summary, summaryLength), person.tag)
+			: null,
+		url: url,
+		fields,
+		birthday: bday ? bday[0] : null,
+		location: person["vcard:Address"] || null,
+		userHost: host,
+	});
+
+	const publicKey = person.publicKey
+		? new UserPublickey({
+			userId: user.id,
+			keyId: person.publicKey.id,
+			keyPem: person.publicKey.publicKeyPem,
+		})
+		: null;
+
 	try {
-		// Start transaction
+		// Save the objects atomically using a db transaction, note that we should never run any code in a transaction block directly
 		await db.transaction(async (transactionalEntityManager) => {
-			user = (await transactionalEntityManager.save(
-				new User({
-					id: genId(),
-					avatarId: null,
-					bannerId: null,
-					createdAt: new Date(),
-					lastFetchedAt: new Date(),
-					name: truncate(person.name, nameLength),
-					isLocked: !!person.manuallyApprovesFollowers,
-					movedToUri: person.movedTo,
-					alsoKnownAs: person.alsoKnownAs,
-					isExplorable: !!person.discoverable,
-					username: person.preferredUsername,
-					usernameLower: person.preferredUsername!.toLowerCase(),
-					host,
-					inbox: person.inbox,
-					sharedInbox:
-						person.sharedInbox ||
-						(person.endpoints ? person.endpoints.sharedInbox : undefined),
-					followersUri: person.followers
-						? getApId(person.followers)
-						: undefined,
-					followersCount:
-						followersCount !== undefined
-							? followersCount
-							: person.followers &&
-							  typeof person.followers !== "string" &&
-							  isCollectionOrOrderedCollection(person.followers)
-							? person.followers.totalItems
-							: undefined,
-					followingCount:
-						followingCount !== undefined
-							? followingCount
-							: person.following &&
-							  typeof person.following !== "string" &&
-							  isCollectionOrOrderedCollection(person.following)
-							? person.following.totalItems
-							: undefined,
-					featured: person.featured ? getApId(person.featured) : undefined,
-					uri: person.id,
-					tags,
-					isBot,
-					isCat: (person as any).isCat === true,
-				}),
-			)) as IRemoteUser;
-
-			await transactionalEntityManager.save(
-				new UserProfile({
-					userId: user.id,
-					description: person.summary
-						? await htmlToMfm(truncate(person.summary, summaryLength), person.tag)
-						: null,
-					url: url,
-					fields,
-					birthday: bday ? bday[0] : null,
-					location: person["vcard:Address"] || null,
-					userHost: host,
-				}),
-			);
-
-			if (person.publicKey) {
-				await transactionalEntityManager.save(
-					new UserPublickey({
-						userId: user.id,
-						keyId: person.publicKey.id,
-						keyPem: person.publicKey.publicKeyPem,
-					}),
-				);
-			}
+			await transactionalEntityManager.save(user);
+			await transactionalEntityManager.save(profile);
+			if (publicKey) await transactionalEntityManager.save(publicKey);
 		});
 	} catch (e) {
 		// duplicate key error
@@ -754,21 +751,23 @@ export async function updateFeatured(userId: User["id"], resolver?: Resolver, li
 			.map((item) => limit(() => resolveNote(item, resolver, limiter))),
 	);
 
-	await db.transaction(async (transactionalEntityManager) => {
-		await transactionalEntityManager.delete(UserNotePining, {
+	// Prepare the objects
+	// For now, generate the id at a different time and maintain the order.
+	const data: Partial<UserNotePining>[] = [];
+	let td = 0;
+	for (const note of featuredNotes.filter((note) => note != null)) {
+		td -= 1000;
+		data.push({
+			id: genId(new Date(Date.now() + td)),
+			createdAt: new Date(),
 			userId: user.id,
+			noteId: note!.id,
 		});
+	}
 
-		// For now, generate the id at a different time and maintain the order.
-		let td = 0;
-		for (const note of featuredNotes.filter((note) => note != null)) {
-			td -= 1000;
-			transactionalEntityManager.insert(UserNotePining, {
-				id: genId(new Date(Date.now() + td)),
-				createdAt: new Date(),
-				userId: user.id,
-				noteId: note!.id,
-			});
-		}
+	// Save the objects atomically using a db transaction, note that we should never run any code in a transaction block directly
+	await db.transaction(async (transactionalEntityManager) => {
+		await transactionalEntityManager.delete(UserNotePining, { userId: user.id });
+		await transactionalEntityManager.insert(UserNotePining, data);
 	});
 }
diff --git a/packages/backend/src/server/api/common/signup.ts b/packages/backend/src/server/api/common/signup.ts
index 6beae2c78..19d4f17aa 100644
--- a/packages/backend/src/server/api/common/signup.ts
+++ b/packages/backend/src/server/api/common/signup.ts
@@ -84,58 +84,55 @@ export async function signup(opts: {
 		),
 	);
 
-	let account!: User;
-
-	// Start transaction
-	await db.transaction(async (transactionalEntityManager) => {
-		const exist = await transactionalEntityManager.findOneBy(User, {
-			usernameLower: username.toLowerCase(),
-			host: IsNull(),
-		});
-
-		if (exist) throw new Error(" the username is already used");
-
-		account = await transactionalEntityManager.save(
-			new User({
-				id: genId(),
-				createdAt: new Date(),
-				username: username,
-				usernameLower: username.toLowerCase(),
-				host: toPunyNullable(host),
-				token: secret,
-				isAdmin:
-					(await Users.countBy({
-						host: IsNull(),
-						isAdmin: true,
-					})) === 0,
-			}),
-		);
-
-		await transactionalEntityManager.save(
-			new UserKeypair({
-				publicKey: keyPair[0],
-				privateKey: keyPair[1],
-				userId: account.id,
-			}),
-		);
-
-		await transactionalEntityManager.save(
-			new UserProfile({
-				userId: account.id,
-				autoAcceptFollowed: true,
-				password: hash,
-			}),
-		);
-
-		await transactionalEntityManager.save(
-			new UsedUsername({
-				createdAt: new Date(),
-				username: username.toLowerCase(),
-			}),
-		);
+	const exist = await Users.findOneBy({
+		usernameLower: username.toLowerCase(),
+		host: IsNull(),
 	});
 
-	usersChart.update(account, true);
+	if (exist) throw new Error("The username is already in use");
 
+	// Prepare objects
+	const user = new User({
+		id: genId(),
+		createdAt: new Date(),
+		username: username,
+		usernameLower: username.toLowerCase(),
+		host: toPunyNullable(host),
+		token: secret,
+		isAdmin:
+			(await Users.countBy({
+				host: IsNull(),
+				isAdmin: true,
+			})) === 0,
+	});
+
+	const userKeypair = new UserKeypair({
+		publicKey: keyPair[0],
+		privateKey: keyPair[1],
+		userId: user.id,
+	});
+
+	const userProfile = new UserProfile({
+		userId: user.id,
+		autoAcceptFollowed: true,
+		password: hash,
+	});
+
+	const usedUsername = new UsedUsername({
+		createdAt: new Date(),
+		username: username.toLowerCase(),
+	});
+
+	// Save the objects atomically using a db transaction, note that we should never run any code in a transaction block directly
+	await db.transaction(async (transactionalEntityManager) => {
+		await transactionalEntityManager.save(user);
+		await transactionalEntityManager.save(userKeypair);
+		await transactionalEntityManager.save(userProfile);
+		await transactionalEntityManager.save(usedUsername);
+	});
+
+	const account = await Users.findOneByOrFail({ id: user.id });
+
+	usersChart.update(account, true);
 	return { account, secret };
 }
diff --git a/packages/backend/src/server/api/endpoints/admin/accounts/hosted.ts b/packages/backend/src/server/api/endpoints/admin/accounts/hosted.ts
index a7b6e95c2..a5423e154 100644
--- a/packages/backend/src/server/api/endpoints/admin/accounts/hosted.ts
+++ b/packages/backend/src/server/api/endpoints/admin/accounts/hosted.ts
@@ -3,6 +3,7 @@ import { Meta } from "@/models/entities/meta.js";
 import { insertModerationLog } from "@/services/insert-moderation-log.js";
 import { db } from "@/db/postgre.js";
 import define from "../../../define.js";
+import { Metas } from "@/models/index.js";
 
 export const meta = {
 	tags: ["admin"],
@@ -106,21 +107,19 @@ export default define(meta, paramDef, async (ps, me) => {
 		if (config.summalyProxyUrl !== undefined) {
 			set.summalyProxy = config.summalyProxyUrl;
 		}
-		await db.transaction(async (transactionalEntityManager) => {
-			const metas = await transactionalEntityManager.find(Meta, {
-				order: {
-					id: "DESC",
-				},
-			});
 
-			const meta = metas[0];
-
-			if (meta) {
-				await transactionalEntityManager.update(Meta, meta.id, set);
-			} else {
-				await transactionalEntityManager.save(Meta, set);
-			}
+		const meta = await Metas.findOne({
+			where: {},
+			order: {
+				id: "DESC",
+			},
 		});
+
+		if (meta)
+			await Metas.update(meta.id, set);
+		else
+			await Metas.save(set);
+
 		insertModerationLog(me, "updateMeta");
 	}
 	return hosted;
diff --git a/packages/backend/src/server/api/endpoints/admin/update-meta.ts b/packages/backend/src/server/api/endpoints/admin/update-meta.ts
index 89f657ef4..e4f9b51a7 100644
--- a/packages/backend/src/server/api/endpoints/admin/update-meta.ts
+++ b/packages/backend/src/server/api/endpoints/admin/update-meta.ts
@@ -2,6 +2,7 @@ import { Meta } from "@/models/entities/meta.js";
 import { insertModerationLog } from "@/services/insert-moderation-log.js";
 import { db } from "@/db/postgre.js";
 import define from "../../define.js";
+import { Metas } from "@/models/index.js";
 
 export const meta = {
 	tags: ["admin"],
@@ -546,21 +547,17 @@ export default define(meta, paramDef, async (ps, me) => {
 		}
 	}
 
-	await db.transaction(async (transactionalEntityManager) => {
-		const metas = await transactionalEntityManager.find(Meta, {
-			order: {
-				id: "DESC",
-			},
-		});
-
-		const meta = metas[0];
-
-		if (meta) {
-			await transactionalEntityManager.update(Meta, meta.id, set);
-		} else {
-			await transactionalEntityManager.save(Meta, set);
-		}
+	const meta = await Metas.findOne({
+		where: {},
+		order: {
+			id: "DESC",
+		},
 	});
 
+	if (meta)
+		await Metas.update(meta.id, set);
+	else
+		await Metas.save(set);
+
 	insertModerationLog(me, "updateMeta");
 });
diff --git a/packages/backend/src/services/create-system-user.ts b/packages/backend/src/services/create-system-user.ts
index 24536090a..60901e186 100644
--- a/packages/backend/src/services/create-system-user.ts
+++ b/packages/backend/src/services/create-system-user.ts
@@ -9,8 +9,9 @@ import { UserKeypair } from "@/models/entities/user-keypair.js";
 import { UsedUsername } from "@/models/entities/used-username.js";
 import { db } from "@/db/postgre.js";
 import { hashPassword } from "@/misc/password.js";
+import { Users } from "@/models/index.js";
 
-export async function createSystemUser(username: string) {
+export async function createSystemUser(username: string): Promise<User> {
 	const password = uuid();
 
 	// Generate hash of password
@@ -23,49 +24,51 @@ export async function createSystemUser(username: string) {
 
 	let account!: User;
 
-	// Start transaction
-	await db.transaction(async (transactionalEntityManager) => {
-		const exist = await transactionalEntityManager.findOneBy(User, {
-			usernameLower: username.toLowerCase(),
-			host: IsNull(),
-		});
-
-		if (exist) throw new Error("the user is already exists");
-
-		account = await transactionalEntityManager
-			.insert(User, {
-				id: genId(),
-				createdAt: new Date(),
-				username: username,
-				usernameLower: username.toLowerCase(),
-				host: null,
-				token: secret,
-				isAdmin: false,
-				isLocked: true,
-				isExplorable: false,
-				isBot: true,
-			})
-			.then((x) =>
-				transactionalEntityManager.findOneByOrFail(User, x.identifiers[0]),
-			);
-
-		await transactionalEntityManager.insert(UserKeypair, {
-			publicKey: keyPair.publicKey,
-			privateKey: keyPair.privateKey,
-			userId: account.id,
-		});
-
-		await transactionalEntityManager.insert(UserProfile, {
-			userId: account.id,
-			autoAcceptFollowed: false,
-			password: hash,
-		});
-
-		await transactionalEntityManager.insert(UsedUsername, {
-			createdAt: new Date(),
-			username: username.toLowerCase(),
-		});
+	const exist = await Users.findOneBy({
+		usernameLower: username.toLowerCase(),
+		host: IsNull(),
 	});
 
-	return account;
+	if (exist) throw new Error("the user is already exists");
+
+	// Prepare objects
+	const user = {
+		id: genId(),
+		createdAt: new Date(),
+		username: username,
+		usernameLower: username.toLowerCase(),
+		host: null,
+		token: secret,
+		isAdmin: false,
+		isLocked: true,
+		isExplorable: false,
+		isBot: true,
+	};
+
+	const userKeypair = {
+		publicKey: keyPair.publicKey,
+		privateKey: keyPair.privateKey,
+		userId: user.id,
+	};
+
+	const userProfile = {
+		userId: user.id,
+		autoAcceptFollowed: false,
+		password: hash,
+	};
+
+	const usedUsername = {
+		createdAt: new Date(),
+		username: username.toLowerCase(),
+	}
+
+	// Save the objects atomically using a db transaction, note that we should never run any code in a transaction block directly
+	await db.transaction(async (transactionalEntityManager) => {
+		await transactionalEntityManager.insert(User, user);
+		await transactionalEntityManager.insert(UserKeypair, userKeypair);
+		await transactionalEntityManager.insert(UserProfile, userProfile);
+		await transactionalEntityManager.insert(UsedUsername, usedUsername);
+	});
+
+	return Users.findOneByOrFail({ id: user.id });
 }
diff --git a/packages/backend/src/services/note/create.ts b/packages/backend/src/services/note/create.ts
index 9a549dfa2..c41897c34 100644
--- a/packages/backend/src/services/note/create.ts
+++ b/packages/backend/src/services/note/create.ts
@@ -756,30 +756,30 @@ async function insertNote(
 	// 投稿を作成
 	try {
 		if (insert.hasPoll) {
-			// Start transaction
+			// Prepare objects
+			if (!data.poll) throw new Error("Empty poll data");
+
+			let expiresAt: Date | null;
+			if (!data.poll.expiresAt || isNaN(data.poll.expiresAt.getTime())) {
+				expiresAt = null;
+			} else {
+				expiresAt = data.poll.expiresAt;
+			}
+
+			const poll = new Poll({
+				noteId: insert.id,
+				choices: data.poll.choices,
+				expiresAt,
+				multiple: data.poll.multiple,
+				votes: new Array(data.poll.choices.length).fill(0),
+				noteVisibility: insert.visibility,
+				userId: user.id,
+				userHost: user.host,
+			});
+
+			// Save the objects atomically using a db transaction, note that we should never run any code in a transaction block directly
 			await db.transaction(async (transactionalEntityManager) => {
-				if (!data.poll) throw new Error("Empty poll data");
-
 				await transactionalEntityManager.insert(Note, insert);
-
-				let expiresAt: Date | null;
-				if (!data.poll.expiresAt || isNaN(data.poll.expiresAt.getTime())) {
-					expiresAt = null;
-				} else {
-					expiresAt = data.poll.expiresAt;
-				}
-
-				const poll = new Poll({
-					noteId: insert.id,
-					choices: data.poll.choices,
-					expiresAt,
-					multiple: data.poll.multiple,
-					votes: new Array(data.poll.choices.length).fill(0),
-					noteVisibility: insert.visibility,
-					userId: user.id,
-					userHost: user.host,
-				});
-
 				await transactionalEntityManager.insert(Poll, poll);
 			});
 		} else {