Scaling React Native for Performance: Lessons From a Real-World App

After scaling a React Native app from prototype to production with thousands of daily active users, I’ve learned that performance issues are rarely the framework’s fault. They’re usually our fault. Here are the optimization strategies that actually moved the needle.

1. FlatList Is Non-Negotiable

For any list with more than 10 items, FlatList should be your go-to component. Unlike ScrollView, FlatList only renders items that are visible on screen, dramatically improving performance.

<FlatList
  data={items}
  keyExtractor={(item) => item.id.toString()}
  renderItem={({ item }) => <ListItem item={item} />}
  initialNumToRender={10}
  windowSize={5}
/>

Key parameters:

• initialNumToRender: Controls how many items render on initial load
• windowSize: Determines how many screens worth of content to keep in memory

2. Memoization Fixes Re-Renders

Prevent unnecessary re-renders of list items by using React.memo:

const ListItem = React.memo(({ item }) => {
  return <Text>{item.name}</Text>;
});

Additionally, use useCallback and useMemo hooks to stabilize props and prevent child component re-renders.

3. Lazy Load Screens and Expensive Components

Don’t load everything at once. Conditionally render heavy components:

// Lazy load screens
const LazyComponent = React.lazy(() => import('./HeavyScreen'));

// Conditional rendering
{showVideo && <VideoPlayer />}

This ensures expensive components only mount when actually needed.

4. Use InteractionManager to Defer Work

Defer non-critical tasks until after animations and interactions complete:

useEffect(() => {
  const task = InteractionManager.runAfterInteractions(() => {
    // Perform heavy computations or API calls here
  });
  
  return () => task.cancel();
}, []);

This keeps the UI responsive during user interactions.

5. Image Optimization

Images are often the biggest performance culprit. Use react-native-fast-image for caching and priority loading:

import FastImage from 'react-native-fast-image';

<FastImage
  style={{ width: 100, height: 100 }}
  source={{ 
    uri: imageUrl, 
    priority: FastImage.priority.high 
  }}
  resizeMode={FastImage.resizeMode.cover}
/>

Additional tips:

• Compress images before uploading
• Use appropriate image formats (WebP when possible)
• Implement progressive loading for large images

6. Animations with Reanimated

For smooth 60fps animations, use react-native-reanimated which runs on the UI thread:

import Animated, {
  useSharedValue,
  useAnimatedStyle,
  withSpring,
} from 'react-native-reanimated';

const offset = useSharedValue(0);

const animatedStyle = useAnimatedStyle(() => ({
  transform: [{ translateY: withSpring(offset.value) }],
}));

This approach avoids bridge communication and ensures buttery-smooth animations.

7. Simplify View Hierarchies

Over-nesting Views creates performance bottlenecks. Keep your component trees shallow:

// Bad
<View>
  <View>
    <View>
      <Text>Content</Text>
    </View>
  </View>
</View>

// Good
<View>
  <Text>Content</Text>
</View>

Use React DevTools to identify and eliminate unnecessary nesting.

8. Monitor Bundle Size

Regularly audit your JavaScript bundle:

• Remove unused dependencies
• Use dynamic imports for code splitting
• Analyze bundle composition with tools like react-native-bundle-visualizer

Key Takeaways

React Native can deliver native-level performance when properly optimized. The key is understanding the framework’s strengths and limitations, then implementing these proven optimization techniques.

Remember: most performance issues are developer-created and can be resolved with strategic optimization. Start with FlatList, add memoization, optimize images, and keep your view hierarchies simple. Your users (and your app store ratings) will thank you.