Duolingo + KMP: A Case Study in Developer Productivity
Article Summary
Duolingo ships weekly to 40M+ daily active users across 176 countries. Their secret weapon for speed? Kotlin Multiplatform.
John Rodriguez and Johnny Ye from Duolingo share how their team evolved from experimenting with React Native and Flutter to making KMP their go-to solution for cross-platform features. This is a candid look at what worked, what didn't, and how they got buy-in across iOS, Android, and backend teams.
Key Takeaways
- First KMP project (experiments library) never shipped but paid crucial explorer's tax
- Adventures took 9 months on Android, 5 months for KMP port, just 1.5 for web
- Math grading library: 1.5 months to build, 1 week each to backport iOS and Android
- Maker project went KMP first, delivered 180+ video variants as JSON instead of MP4s
- Performance on iOS matched native app despite heavy animation and frame-by-frame updates
Critical Insight
Duolingo's KMP journey shows that initial projects take longer, but subsequent features ship 5-10x faster once the infrastructure and team knowledge are in place.
