expo-react-native-performance

Expo React Native Performance Best Practices Comprehensive performance optimization guide for Expo React Native applications. Contains 42 rules across 8 categories, prioritized by impact to guide automated refactoring and code generation. When to Apply Reference these guidelines when: Writing new React Native components or screens Implementing lists with FlatList or FlashList Adding animations or transitions Optimizing images and asset loading Reviewing code for performance issues Rule Categories by Priority Priority Category Impact Prefix 1 App Startup & Bundle Size CRITICAL startup- 2 List Virtualization CRITICAL list- 3 Re-render Optimization HIGH rerender- 4 Animation Performance HIGH anim- 5 Image & Asset Loading MEDIUM-HIGH asset- 6 Memory Management MEDIUM mem- 7 Async & Data Fetching MEDIUM async- 8 Platform Optimizations LOW-MEDIUM platform- Quick Reference 1. App Startup & Bundle Size (CRITICAL) startup-enable-hermes - Enable Hermes JavaScript engine startup-remove-console-logs - Remove console logs in production startup-splash-screen-control - Control splash screen visibility startup-preload-assets - Preload critical assets during splash startup-async-routes - Use async routes for code splitting startup-cherry-pick-imports - Use direct imports instead of barrel files 2. List Virtualization (CRITICAL) list-use-flashlist - Use FlashList instead of FlatList list-estimated-item-size - Provide accurate estimatedItemSize list-get-item-type - Use getItemType for mixed lists list-stable-render-item - Stabilize renderItem with useCallback list-get-item-layout - Provide getItemLayout for fixed heights list-memoize-items - Memoize list item components 3. Re-render Optimization (HIGH) rerender-use-memo-expensive - Memoize expensive computations rerender-use-callback-handlers - Stabilize callbacks with useCallback rerender-functional-setstate - Use functional setState updates rerender-lazy-state-init - Use lazy state initialization rerender-split-context - Split context by update frequency rerender-derive-state - Derive state instead of syncing 4. Animation Performance (HIGH) anim-use-native-driver - Enable native driver for animations anim-use-reanimated - Use Reanimated for complex animations anim-layout-animation - Use LayoutAnimation for simple transitions anim-transform-not-dimensions - Animate transform instead of dimensions anim-interaction-manager - Defer heavy work during animations 5. Image & Asset Loading (MEDIUM-HIGH) asset-use-expo-image - Use expo-image for image loading asset-prefetch-images - Prefetch images before display asset-optimize-image-size - Request appropriately sized images asset-use-webp-format - Use WebP format for images asset-recycling-key - Use recyclingKey in FlashList images 6. Memory Management (MEDIUM) mem-cleanup-subscriptions - Clean up subscriptions in useEffect mem-clear-timers - Clear timers on unmount mem-abort-fetch - Abort fetch requests on unmount mem-avoid-inline-objects - Avoid inline objects in props mem-limit-list-data - Limit list data in memory 7. Async & Data Fetching (MEDIUM) async-parallel-fetching - Fetch independent data in parallel async-defer-await - Defer await until value needed async-batch-api-calls - Batch related API calls async-cache-responses - Cache API responses locally async-refetch-on-focus - Refetch data on screen focus 8. Platform Optimizations (LOW-MEDIUM) platform-android-overdraw - Reduce Android overdraw platform-ios-text-rendering - Optimize iOS text rendering platform-android-proguard - Enable ProGuard for Android release platform-conditional-render - Platform-specific optimizations How to Use Read individual reference files for detailed explanations and code examples: Section definitions - Category structure and impact levels Rule template - Template for adding new rules Full Compiled Document For the complete guide with all rules expanded, see AGENTS.md . Reference Files File Description AGENTS.md Complete compiled guide with all rules references/_sections.md Category definitions and ordering assets/templates/_template.md Template for new rules metadata.json Version and reference information