From 3868c0cf4eb133ac365076b792e4046f4ca51ebf Mon Sep 17 00:00:00 2001
From: Mohammad Faiz <mohdfaiz2k9@gmail.com>
Date: Thu, 5 Mar 2026 21:05:14 +0530
Subject: [PATCH] Delete skills/performance-optimizer

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 skills/performance-optimizer | 389 -----------------------------------
 1 file changed, 389 deletions(-)
 delete mode 100644 skills/performance-optimizer

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----
-name: performance-optimizer
-description: "Identifies and fixes performance bottlenecks in code, databases, and APIs. Measures before and after to prove improvements."
-category: development
-risk: safe
-source: community
-date_added: "2026-03-05"
----
-
-# Performance Optimizer
-
-Find and fix performance bottlenecks. Measure, optimize, verify. Make it fast.
-
-## When to Use This Skill
-
-- App is slow or laggy
-- User complains about performance
-- Page load times are high
-- API responses are slow
-- Database queries take too long
-- User mentions "slow", "lag", "performance", or "optimize"
-
-## The Optimization Process
-
-### 1. Measure First
-
-Never optimize without measuring:
-
-```javascript
-// Measure execution time
-console.time('operation');
-await slowOperation();
-console.timeEnd('operation'); // operation: 2341ms
-```
-
-**What to measure:**
-- Page load time
-- API response time
-- Database query time
-- Function execution time
-- Memory usage
-- Network requests
-
-### 2. Find the Bottleneck
-
-Use profiling tools to find the slow parts:
-
-**Browser:**
-```
-DevTools → Performance tab → Record → Stop
-Look for long tasks (red bars)
-```
-
-**Node.js:**
-```bash
-node --prof app.js
-node --prof-process isolate-*.log > profile.txt
-```
-
-**Database:**
-```sql
-EXPLAIN ANALYZE SELECT * FROM users WHERE email = 'test@example.com';
-```
-
-### 3. Optimize
-
-Fix the slowest thing first (biggest impact).
-
-## Common Optimizations
-
-### Database Queries
-
-**Problem: N+1 Queries**
-```javascript
-// Bad: N+1 queries
-const users = await db.users.find();
-for (const user of users) {
-  user.posts = await db.posts.find({ userId: user.id }); // N queries
-}
-
-// Good: Single query with JOIN
-const users = await db.users.find()
-  .populate('posts'); // 1 query
-```
-
-**Problem: Missing Index**
-```sql
--- Check slow query
-EXPLAIN SELECT * FROM users WHERE email = 'test@example.com';
--- Shows: Seq Scan (bad)
-
--- Add index
-CREATE INDEX idx_users_email ON users(email);
-
--- Check again
-EXPLAIN SELECT * FROM users WHERE email = 'test@example.com';
--- Shows: Index Scan (good)
-```
-
-**Problem: SELECT ***
-```javascript
-// Bad: Fetches all columns
-const users = await db.query('SELECT * FROM users');
-
-// Good: Only needed columns
-const users = await db.query('SELECT id, name, email FROM users');
-```
-
-**Problem: No Pagination**
-```javascript
-// Bad: Returns all records
-const users = await db.users.find();
-
-// Good: Paginated
-const users = await db.users.find()
-  .limit(20)
-  .skip((page - 1) * 20);
-```
-
-### API Performance
-
-**Problem: No Caching**
-```javascript
-// Bad: Hits database every time
-app.get('/api/stats', async (req, res) => {
-  const stats = await db.stats.calculate(); // Slow
-  res.json(stats);
-});
-
-// Good: Cache for 5 minutes
-const cache = new Map();
-app.get('/api/stats', async (req, res) => {
-  const cached = cache.get('stats');
-  if (cached && Date.now() - cached.time < 300000) {
-    return res.json(cached.data);
-  }
-  
-  const stats = await db.stats.calculate();
-  cache.set('stats', { data: stats, time: Date.now() });
-  res.json(stats);
-});
-```
-
-**Problem: Sequential Operations**
-```javascript
-// Bad: Sequential (slow)
-const user = await getUser(id);
-const posts = await getPosts(id);
-const comments = await getComments(id);
-// Total: 300ms + 200ms + 150ms = 650ms
-
-// Good: Parallel (fast)
-const [user, posts, comments] = await Promise.all([
-  getUser(id),
-  getPosts(id),
-  getComments(id)
-]);
-// Total: max(300ms, 200ms, 150ms) = 300ms
-```
-
-**Problem: Large Payloads**
-```javascript
-// Bad: Returns everything
-res.json(users); // 5MB response
-
-// Good: Only needed fields
-res.json(users.map(u => ({
-  id: u.id,
-  name: u.name,
-  email: u.email
-}))); // 500KB response
-```
-
-### Frontend Performance
-
-**Problem: Unnecessary Re-renders**
-```javascript
-// Bad: Re-renders on every parent update
-function UserList({ users }) {
-  return users.map(user => <UserCard user={user} />);
-}
-
-// Good: Memoized
-const UserCard = React.memo(({ user }) => {
-  return <div>{user.name}</div>;
-});
-```
-
-**Problem: Large Bundle**
-```javascript
-// Bad: Imports entire library
-import _ from 'lodash'; // 70KB
-
-// Good: Import only what you need
-import debounce from 'lodash/debounce'; // 2KB
-```
-
-**Problem: No Code Splitting**
-```javascript
-// Bad: Everything in one bundle
-import HeavyComponent from './HeavyComponent';
-
-// Good: Lazy load
-const HeavyComponent = React.lazy(() => import('./HeavyComponent'));
-```
-
-**Problem: Unoptimized Images**
-```html
-<!-- Bad: Large image -->
-<img src="photo.jpg" /> <!-- 5MB -->
-
-<!-- Good: Optimized and responsive -->
-<img 
-  src="photo-small.webp" 
-  srcset="photo-small.webp 400w, photo-large.webp 800w"
-  loading="lazy"
-  width="400"
-  height="300"
-/> <!-- 50KB -->
-```
-
-### Algorithm Optimization
-
-**Problem: Inefficient Algorithm**
-```javascript
-// Bad: O(n²) - nested loops
-function findDuplicates(arr) {
-  const duplicates = [];
-  for (let i = 0; i < arr.length; i++) {
-    for (let j = i + 1; j < arr.length; j++) {
-      if (arr[i] === arr[j]) duplicates.push(arr[i]);
-    }
-  }
-  return duplicates;
-}
-
-// Good: O(n) - single pass with Set
-function findDuplicates(arr) {
-  const seen = new Set();
-  const duplicates = new Set();
-  for (const item of arr) {
-    if (seen.has(item)) duplicates.add(item);
-    seen.add(item);
-  }
-  return Array.from(duplicates);
-}
-```
-
-**Problem: Repeated Calculations**
-```javascript
-// Bad: Calculates every time
-function getTotal(items) {
-  return items.reduce((sum, item) => sum + item.price * item.quantity, 0);
-}
-// Called 100 times in render
-
-// Good: Memoized
-const getTotal = useMemo(() => {
-  return items.reduce((sum, item) => sum + item.price * item.quantity, 0);
-}, [items]);
-```
-
-### Memory Optimization
-
-**Problem: Memory Leak**
-```javascript
-// Bad: Event listener not cleaned up
-useEffect(() => {
-  window.addEventListener('scroll', handleScroll);
-  // Memory leak!
-}, []);
-
-// Good: Cleanup
-useEffect(() => {
-  window.addEventListener('scroll', handleScroll);
-  return () => window.removeEventListener('scroll', handleScroll);
-}, []);
-```
-
-**Problem: Large Data in Memory**
-```javascript
-// Bad: Loads entire file into memory
-const data = fs.readFileSync('huge-file.txt'); // 1GB
-
-// Good: Stream it
-const stream = fs.createReadStream('huge-file.txt');
-stream.on('data', chunk => process(chunk));
-```
-
-## Measuring Impact
-
-Always measure before and after:
-
-```javascript
-// Before optimization
-console.time('query');
-const users = await db.users.find();
-console.timeEnd('query');
-// query: 2341ms
-
-// After optimization (added index)
-console.time('query');
-const users = await db.users.find();
-console.timeEnd('query');
-// query: 23ms
-
-// Improvement: 100x faster!
-```
-
-## Performance Budgets
-
-Set targets:
-
-```
-Page Load: < 2 seconds
-API Response: < 200ms
-Database Query: < 50ms
-Bundle Size: < 200KB
-Time to Interactive: < 3 seconds
-```
-
-## Tools
-
-**Browser:**
-- Chrome DevTools Performance tab
-- Lighthouse (audit)
-- Network tab (waterfall)
-
-**Node.js:**
-- `node --prof` (profiling)
-- `clinic` (diagnostics)
-- `autocannon` (load testing)
-
-**Database:**
-- `EXPLAIN ANALYZE` (query plans)
-- Slow query log
-- Database profiler
-
-**Monitoring:**
-- New Relic
-- Datadog
-- Sentry Performance
-
-## Quick Wins
-
-Easy optimizations with big impact:
-
-1. **Add database indexes** on frequently queried columns
-2. **Enable gzip compression** on server
-3. **Add caching** for expensive operations
-4. **Lazy load** images and heavy components
-5. **Use CDN** for static assets
-6. **Minify and compress** JavaScript/CSS
-7. **Remove unused dependencies**
-8. **Use pagination** instead of loading all data
-9. **Optimize images** (WebP, proper sizing)
-10. **Enable HTTP/2** on server
-
-## Optimization Checklist
-
-- [ ] Measured current performance
-- [ ] Identified bottleneck
-- [ ] Applied optimization
-- [ ] Measured improvement
-- [ ] Verified functionality still works
-- [ ] No new bugs introduced
-- [ ] Documented the change
-
-## When NOT to Optimize
-
-- Premature optimization (optimize when it's actually slow)
-- Micro-optimizations (save 1ms when page takes 5 seconds)
-- Readable code is more important than tiny speed gains
-- If it's already fast enough
-
-## Key Principles
-
-- Measure before optimizing
-- Fix the biggest bottleneck first
-- Measure after to prove improvement
-- Don't sacrifice readability for tiny gains
-- Profile in production-like environment
-- Consider the 80/20 rule (20% of code causes 80% of slowness)
-
-## Related Skills
-
-- `@database-design` - Query optimization
-- `@codebase-audit-pre-push` - Code review
-- `@bug-hunter` - Debugging