Crossing the React Native / native boundary intentionally

One misconception about using React Native and Expo is that cross-platform development means never writing native code.

In reality, some product requirements are deeply connected to the operating system or hardware. Payment terminals, printers, background services and device-specific SDKs often require you to cross the JavaScript/native boundary.

I encountered this while working on a React Native project that needed to communicate with specialised Android hardware. My approach was to create:

• A small native Android module for communicating with the device
• A typed TypeScript interface for the React Native layer
• An Expo config plugin to reproduce the native setup during prebuild
• A fallback for devices where the hardware was unavailable

The main lesson was to keep the native surface area small. Most of the application remained cross-platform, while the hardware-specific logic stayed behind a clear interface.

Cross-platform development is not about avoiding native code completely. It is about using it intentionally.