Building Offline-First Apps with KMP

Users expect apps to work without internet. At MBS, every product we build is offline-first by default. Here are the architecture patterns and implementation strategies we use in Kotlin Multiplatform.

The Offline-First Architecture

Our pattern is simple: local database is the single source of truth. UI reads from local storage (SQLDelight). Network requests update local storage. The UI reactively updates via Kotlin Flows. This means the app works instantly on launch, even without connectivity.

Sync Strategies

We use three sync patterns depending on the data type: pull-on-demand for user-triggered refreshes, periodic background sync for feeds and catalogs, and optimistic writes for user actions (like/save/download). Each pattern has different conflict resolution — last-write-wins for simple data, merge for complex entities.

Implementation with SQLDelight + Ktor

SQLDelight handles local persistence with type-safe queries and automatic migrations. Ktor Client handles API calls with retry logic and exponential backoff. A shared Repository layer coordinates between them, exposing Flows that emit cached data immediately and fresh data when available. This entire stack is shared across all platforms.