diff --git a/packages/backend/migration/1675375940759-registry-remove-domain.js b/packages/backend/migration/1675375940759-registry-remove-domain.js
new file mode 100644
index 000000000..50a6f6b8b
--- /dev/null
+++ b/packages/backend/migration/1675375940759-registry-remove-domain.js
@@ -0,0 +1,19 @@
+export class registryRemoveDomain1675375940759 {
+    name = 'registryRemoveDomain1675375940759'
+
+    async up(queryRunner) {
+        await queryRunner.query(`DROP INDEX "public"."IDX_0a72bdfcdb97c0eca11fe7ecad"`);
+        await queryRunner.query(`ALTER TABLE "registry_item" DROP COLUMN "domain"`);
+        await queryRunner.query(`ALTER TABLE "registry_item" ALTER COLUMN "key" TYPE text USING "key"::text`);
+        // delete existing duplicated entries, keeping the latest updated one
+        await queryRunner.query(`DELETE FROM "registry_item" AS "a" WHERE "updatedAt" != (SELECT MAX("updatedAt") OVER (PARTITION BY "userId", "key", "scope") FROM "registry_item" AS "b" WHERE "a"."userId" = "b"."userId" AND "a"."key" = "b"."key" AND "a"."scope" = "b"."scope")`);
+        await queryRunner.query(`ALTER TABLE "registry_item" ADD CONSTRAINT "UQ_b8d6509f847331273ab99daccc7" UNIQUE ("userId", "key", "scope")`);
+    }
+
+    async down(queryRunner) {
+        await queryRunner.query(`ALTER TABLE "registry_item" DROP CONSTRAINT "UQ_b8d6509f847331273ab99daccc7"`);
+        await queryRunner.query(`ALTER TABLE "registry_item" ALTER COLUMN "key" TYPE character varying(1024) USING "key"::varchar(1024)`);
+        await queryRunner.query(`ALTER TABLE "registry_item" ADD "domain" character varying(512)`);
+        await queryRunner.query(`CREATE INDEX "IDX_0a72bdfcdb97c0eca11fe7ecad" ON "registry_item" ("domain") `);
+    }
+}
diff --git a/packages/backend/src/models/entities/registry-item.ts b/packages/backend/src/models/entities/registry-item.ts
index e82acb0e4..9ed2af720 100644
--- a/packages/backend/src/models/entities/registry-item.ts
+++ b/packages/backend/src/models/entities/registry-item.ts
@@ -1,9 +1,9 @@
-import { PrimaryColumn, Entity, Index, JoinColumn, Column, ManyToOne } from 'typeorm';
+import { PrimaryColumn, Entity, Index, JoinColumn, Column, ManyToOne, Unique } from 'typeorm';
 import { id } from '../id.js';
 import { User } from './user.js';
 
-// TODO: 同じdomain、同じscope、同じkeyのレコードは二つ以上存在しないように制約付けたい
 @Entity()
+@Unique(['userId', 'key', 'scope'])
 export class RegistryItem {
 	@PrimaryColumn(id())
 	public id: string;
@@ -31,8 +31,7 @@ export class RegistryItem {
 	@JoinColumn()
 	public user: User | null;
 
-	@Column('varchar', {
-		length: 1024,
+	@Column('text', {
 		comment: 'The key of the RegistryItem.',
 	})
 	public key: string;