Improving Swift Compilation Times from 12 to 2 Minutes
Article Summary
Zalando's iOS team was bleeding 12 minutes per build. That's not just annoying, it's expensive.
The Zalando engineering team tackled their growing Swift compilation problem as their Fleek app expanded. A simple Xcode configuration change delivered dramatic results without sacrificing debuggability.
Key Takeaways
- Reduced clean build time from 12 minutes to 2.5 minutes (83% improvement)
- Enabled Whole Module Optimization in Debug without the optimization flag
- Saved 26 hours of daily compilation time across the team
- Used custom SWIFT_WHOLE_MODULE_OPTIMIZATION flag as User-Defined Setting
Critical Insight
A single Xcode build setting change cut compilation time by 80% and saved the equivalent of three full-time developers daily.
