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