Expo SDK 56 ships with a custom Kotlin compiler plugin that eliminates reflection from Expo Modules on Android. The result: 70% faster module initialization and a 30% reduction in time to first render.
The plugin runs during compilation, so app developers get these performance gains automatically without changing any code. Module authors can unlock even bigger wins with a single annotation.
This post walks through how we built it and why this approach succeeded where previous attempts failed. For the Swift side where we now talk to JSI directly, check out our companion post Talking to JSI in Swift.
The reflection problem we inherited
Before Expo Modules, we had Unimodules. They worked like old React Native bridge modules: you'd sprinkle annotations across methods you wanted to expose, and the runtime would discover everything through reflection.
