Swift at Apple: Migrating Password Monitoring Service from Java
Article Summary
Apple's Password Monitoring team just shared something remarkable: they rewrote their entire backend service from Java to Swift and the results are staggering. This isn't a client-side migration story—it's billions of daily server requests getting dramatically faster.
Apple's authentication engineering team migrated their Password Monitoring service (the feature that warns you when your passwords appear in data leaks) from Java to Swift on Linux-based infrastructure. The service handles multiple billions of requests daily with complex cryptographic operations, making performance critical.
Key Takeaways
- 40% throughput increase with sub-1ms latency for 99.9% of requests
- Memory footprint dropped from 10s of gigabytes to 100s of megabytes
- 85% reduction in lines of code while improving readability and safety
- Released 50% of Kubernetes capacity back for other workloads
- Faster bootstrap times enabled dynamic scaling across global traffic patterns
Swift delivered 40% better performance than Java while using 10x less memory, allowing Apple to reclaim half their infrastructure capacity for a service handling billions of daily requests.
