Building a Production-Ready KMP App: Lessons from Mood Movies

Mood Movies is our flagship KMP app — a cross-platform movie discovery experience that matches recommendations to your current mood. Building it taught us invaluable lessons about shipping production-quality KMP apps. Here's what we learned.

Architecture That Scales

We adopted a clean architecture with shared domain and data layers, platform-specific UI where needed, and Koin for dependency injection across all targets. The key was designing the module structure early — shared:core, shared:data, shared:domain, and feature modules for each screen.

Key Technical Decisions

• Ktor for networking: Same HTTP client code on Android, iOS, and desktop with platform-specific engines

• Compose Multiplatform for UI: 85% shared UI with expect/actual for platform-specific components

• Kotlinx Serialization: Type-safe API models shared across all platforms

• Coroutines + Flow: Reactive data streams from API to UI with shared ViewModels

Lessons Learned

The biggest lesson: start with shared business logic, not shared UI. Get your networking, caching, and state management working across platforms first. Then progressively share UI components. This approach reduces risk and lets you validate the shared code path before committing to shared UI.

We teach these exact patterns in our KMP Mastery Course — the same architecture, tools, and decisions that power our production apps. Because we believe the best way to learn is from people who actually ship.