From 30 Minutes Down to 10: Taming our Monolith's CI Build Times

Cash App's monolith CI builds were taking 30 minutes at p50. Developers were stuck waiting through multiple build cycles just to get a green merge.

The Cash App team tackled their legacy 'Franklin' service, a million-line monolith that still powers critical functionality. Despite migrating to microservices, this codebase kept growing and its slow builds were crushing developer productivity.

Key Takeaways

• Cut p50 build times from 30 to 10 minutes, p99 from 45 to 22 minutes
• Modularized codebase to enable Gradle remote build cache with higher hit ratios
• Started test workers eagerly during compilation, saving several minutes per build
• Cached expensive test customer setups, reusing them across hundreds of integration tests
• Distributed 10,000+ tests by historical duration instead of count for balanced shards

The team discovered why simply adding more test workers actually made things worse, not better.