The Fundamentals of iOS Development at Revolut

Revolut ships 3 iOS apps weekly to millions of users. Their secret? A modular architecture that cut build times nearly in half and saves 400 engineering hours monthly.

Revolut's iOS team of 70 engineers manages three apps (Revolut, Junior, and Business) using a sophisticated setup built around speed and reliability. They've moved beyond standard tooling to create custom solutions that keep their financial platform running smoothly across all iOS devices.

Key Takeaways

• Migrated from Xcode to Bazel, cutting builds from 4.2 to 2.64 minutes
• 60 modular components in monorepo enable isolated development and second-long tests
• Feature flags allow instant rollback without new releases or app store delays
• Cross-functional teams own modules end to end, from iOS to backend
• 100% test coverage on core modules with custom framework requiring minimal code

Their approach to avoiding RxSwift and building reactive programming in-house reveals an interesting philosophy about third-party dependencies in fintech.