App Start Demo

A practical React Native (Expo) demo focused on building fast, observable app startups. Before the first screen renders, it manages the critical boot sequence: version gating, maintenance mode, security checks, and splash screen timing. Everything is hooked up to Sentry for full observability, capturing detailed startup traces and navigation telemetry. It also includes a side-by-side look at eager versus lazy loading to show the real-world impact of heavy modules on boot time.

Prerequisites

• Node.js and npm
• Xcode (for iOS builds)
• Android Studio with an Android SDK (for Android builds)

Getting started

• Copy .env.example to .env and fill in the values:

  cp .env.example .env

  Variable	Purpose
  SENTRY_ORG	Your Sentry organization slug. Required by the Expo plugin during the build step.
  SENTRY_PROJECT	Your Sentry project slug. Pairs with your org to route data to the right bucket.
  EXPO_PUBLIC_SENTRY_DSN	Your client key. Baked directly into the JS bundle to power live telemetry and error tracking.

• Install the dependencies:

  npm install

• Generate the native android/ios projects:

  npm run prebuild

• Start the development server:

  npm run start

• Build and run iOS and Android development builds:

  npm run ios
  # or
  npm run android

Code quality

• Run npm run biome:check to catch syntax and formatting issues.
• Use npm run biome:fix to format the codebase and resolve auto-fixable errors.
• npm run ts:check runs a strict type check across the project.
• Run npm test to execute the Jest test suite.