android-data-layer

To build an offline-first data layer, use a Repository pattern to unify Room for local persistence and Retrofit for remote synchronization, establishing a single source of truth. Room handles reactive caching via Flows while Retrofit fetches remote data using suspend functions.

The single source of truth (SSOT) pattern in Android data synchronization uses a local Room database as the primary data source. The Repository observes Room via Flows and updates it through Retrofit background syncs, ensuring the UI always reads reliable cached data.

Handle background sync and conflict resolution using an outbox pattern for deferred remote pushes and stale-while-revalidate strategies. The Repository coordinates Retrofit API calls with Room persistence to manage data conflicts and push pending changes when connectivity restores.

Yes, Hilt dependency injection integrates cleanly with the offline repository pattern. Hilt binds repository interfaces to their Room and Retrofit implementations, enabling testability and clean architecture while managing synchronous and asynchronous data flows across the data layer.

Yes, the offline data layer supports reactive updates through Room Flow-based DAOs. When the Repository updates the local Room database via Retrofit synchronization, Flow automatically propagates changes to the UI, maintaining the single source of truth.

The best way to cache remote API responses locally is using a Repository pattern with Room for persistence and Retrofit for fetching. Stale-while-revalidate strategies fetch fresh data via Retrofit while serving cached Room data instantly, ensuring an offline-first experience.