Screen Response Time: A Critical Metric for User Experience

OkCredit reduced frozen frames by 40% by obsessing over a metric most Android teams ignore: screen response time.

The OkCredit Android team shares their deep dive into measuring and optimizing how fast screens load after a user taps. While web has First Input Delay and Interaction to Next Paint, Android vitals barely scratch the surface on responsiveness metrics.

Key Takeaways

• Target 100ms or less for screen loads to feel instant to users
• XML inflation uses expensive IO operations and reflection for view creation
• Async layout inflation cut screen load by 25% and frozen frames by 30%
• Jetpack Compose loads slower initially but subsequent screens are faster
• 65% of their frozen frames traced back to high input latency

They built custom instrumentation libraries and even explored X2C to eliminate XML parsing entirely—plus a clever MVI trick that parallelizes ViewModel initialization.