performance

name	performance
description	Performance optimization guidelines for React/React Native applications. Use when optimizing app performance, fixing UI freezes/lag, reducing re-renders, handling concurrent operations, or analyzing performance bottlenecks. Triggers on performance, optimization, optimize, slow, lag, freeze, hang, jank, stutter, memory, leak, concurrent, batching, batch, memoization, memo, bridge, windowSize, contentVisibility, FlashList, re-render, fps, tti, bundle.
allowed-tools	Read, Grep, Glob

Performance Optimization

Performance optimization patterns and best practices for React/React Native applications.

Quick Reference

Category	Key Optimization	When to Use
Concurrent Requests	Limit to 3-5, use executeBatched	Multiple API calls, network-heavy operations
Bridge Optimization	Minimize crossings, batch data	React Native bridge overhead, iOS/Android
List Rendering	FlashList, windowSize={5}, content-visibility	Lists with 100+ items
Memoization	memo, useMemo, useCallback	Expensive computations, prevent re-renders
Heavy Operations	InteractionManager, setTimeout	UI blocking operations

Critical Performance Rules

❌ FORBIDDEN: Too Many Concurrent Requests

// ❌ BAD - Can freeze UI with 15+ requests
const requests = items.map(item => fetchData(item));
await Promise.all(requests);

✅ CORRECT: Batched Execution with Concurrency Limit

async function executeBatched<T>(
  tasks: Array<() => Promise<T>>,
  concurrency = 3,
): Promise<Array<PromiseSettledResult<T>>> {
  const results: Array<PromiseSettledResult<T>> = [];
  for (let i = 0; i < tasks.length; i += concurrency) {
    const batch = tasks.slice(i, i + concurrency);
    const batchResults = await Promise.allSettled(
      batch.map((task) => task()),
    );
    results.push(...batchResults);
  }
  return results;
}

const tasks = items.map(item => () => fetchData(item));
await executeBatched(tasks, 3); // Max 3 concurrent

🚨 Built-in Optimizations

Already Optimized - NO ACTION NEEDED:

Component	Optimization	Details
ListView	windowSize={5}	Auto-limits visible items
Tabs	contentVisibility: 'hidden'	Hides inactive tabs
Dialog	contentVisibility: 'hidden'	Hides when closed

Detailed Guide

For comprehensive performance optimization strategies, see performance.md.

Topics covered:

• Concurrent request control
• React Native bridge optimization
• Heavy operations offloading
• List rendering (windowSize, FlashList, content-visibility)
• Memoization & callbacks
• State updates optimization
• Image optimization
• Async operations & race conditions
• Real-world iOS AppHang case study

Related Skills

• /coding-patterns - General coding patterns and conventions
• /sentry-analysis - Sentry error analysis (includes performance issues)
• /react-best-practices - React/React Native optimizations