Slaying the Monolith: API Implementation and Modularization in Android
Article Summary
Sean Coyle from ASOS reveals how they're dismantling their Android monolith using a pattern that slashes recompile times. The secret? Splitting every feature into API and implementation modules.
ASOS's Android team faced the classic monolith problem: slow builds, tangled dependencies, and features that couldn't evolve independently. Coyle walks through their modularization strategy using the API/Implementation pattern, a dependency inversion approach that separates what modules do from how they do it.
Key Takeaways
- API modules expose interfaces only; implementation changes don't trigger full app recompiles
- Pattern follows SOLID's dependency inversion: high-level modules stay stable, low-level modules change freely
- Start with 'leaf nodes' like domain models for easiest extraction from monolith
- Use 'implementation' over 'api' in Gradle to promote encapsulation and faster builds
- Trade-off: Added complexity from managing multiple modules can outweigh benefits in smaller apps
Critical Insight
The API/Implementation pattern enables independent feature evolution and faster compile times by decoupling module contracts from their concrete implementations.
