How Duolingo sped up Android and iOS builds by 68% on CI
Original post How we sped up Android and iOS builds by 68% on CI
Article Summary
Duolingo's Test and Release Infrastructure team just cut mobile CI build times from 50 minutes to 16. That's 68% faster builds across hundreds of PRs per week.
The TRI team at Duolingo tackled a massive developer productivity problem: painfully slow continuous integration checks that ran hundreds of times weekly. Through systematic experimentation with hardware, caching strategies, and toolchain upgrades, they transformed their Android and iOS build pipeline.
Key Takeaways
- Upgraded to AWS r7a instances for Android (21% faster) and M2 Macs for iOS (60% faster)
- Gradle remote S3 cache reduced Android builds 25%, SwiftPM caching saved 4 minutes on iOS
- Migrating from KAPT to KSP plus Kotlin upgrade cut Android CI times another 30%
- Better pipeline parallelization reduced Android serial execution time by 20%
Strategic hardware upgrades, smarter caching, and toolchain modernization slashed mobile CI build times by 68%, dramatically improving developer experience.
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This page summarizes “How we sped up Android and iOS builds by 68% on CI” by Duolingo, published Dec 18, 2024. All credit for the original work goes to the authors.
