name: android-local-storage description: Local storage — Room, DataStore, offline-first architecture, caching, encryption. user-invocable: true

Android Local Storage

Cross-cutting skill — always activates alongside the project-type-specific skill.

Hard Rules

• •Use Room for structured relational data — not raw SQLite.
• •Use DataStore (Preferences or Proto) for key-value data — not SharedPreferences.
• •Export Room schemas (exportSchema = true) and test all migrations.
• •Never perform database operations on the main thread.
• •Use Flow or LiveData for reactive database queries — not one-shot reads for UI.
• •Define a single source of truth (database) — network responses update the database, UI observes the database.
• •Never store sensitive data (tokens, passwords) in Room or DataStore without encryption.
• •Use transactions for multi-table write operations.
• •Keep entities flat — avoid deeply nested objects in Room.
• •Use TypeConverters sparingly — prefer normalized relational design.

Core Patterns

• •Repository pattern: database as the source of truth, network as the updater.
• •Room DAOs return Flow<List<T>> for reactive UI updates.
• •Use @Upsert for insert-or-update operations (Room 2.5+).
• •DataStore with Proto for type-safe structured preferences.
• •Implement cache expiry with timestamps — stale-while-revalidate pattern.
• •Use database-backed pagination with RemoteMediator + Paging 3.

References

• •references/room_patterns.md
• •references/datastore.md
• •references/offline_first.md
• •references/cache_strategies.md
• •references/encryption.md
• •references/migration_testing.md