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name: android-persistence description: Implement Room schemas and DataStore preferences with proper async patterns in Android. Use when the primary task is storage schema, DAO, migration, or preference isolation; defer auth-token/security storage, any CoroutineWorker/WorkManager task, Hilt graph wiring, and cache-policy design. metadata: triggers: files: - '/*Dao.kt' - '/*Database.kt' - '**/*Entity.kt' keywords: - "@Dao" - "@Entity" - RoomDatabase

Android Persistence Standards

Priority: P0 (CRITICAL)

1. Configure Room Database

• Return Flow<List<T>> for queries, use suspend for Write/Insert.
• Keep @Entity data classes simple. Map to Domain models in Repository.
• Use @Transaction for multi-table queries (Relations).

See DAO templates for Room DAO patterns.

2. Migrate to DataStore

• Replace SharedPreferences with ProtoDataStore (type-safe) or PreferencesDataStore.
• Inject singleton DataStore instance via Hilt.

See DAO templates for DataStore migration patterns.

Anti-Patterns

• No IO on Main Thread: Room handles dispatchers, but verify Flow collected off-main.
• No @Entity in UI Layer: Map to Domain or UI models in Repository.

References

• DAO Templates