A hands-on walkthrough of migrating existing native Android (Jetpack Compose) and iOS (SwiftUI) apps to a shared data layer using Room KMP. Starting from the "Fruitties" sample app, we move its Room database into a shared Kotlin Multiplatform module so both platforms read and write the same persistence layer while keeping their native UIs.

We'll cover the full journey: switching to the BundledSQLiteDriver for cross-platform SQLite support, relocating DAOs and entities to commonMain with the Refactor → Move tooling, configuring KSP and the Room Gradle plugin for each platform target, wiring up RoomDatabaseConstructor with expect/actual, and creating an iOS-specific database builder. We then replace the iOS app's Core Data stack with Room — building entity wrappers, updating repositories and dependency injection, and swapping out @FetchRequest in SwiftUI.

Attendees will leave understanding how to share data-layer logic between Android and iOS without rewriting it twice, plus the practical gotchas (binary size, KSP target setup, ObjC naming) to watch for along the way.