Performance Optimization Guide¶

⚡ Optimize web performance using Lighthouse and AI insights¶

Master performance optimization with RapidTriageME's comprehensive auditing and monitoring capabilities.

Performance Metrics Overview¶

Core Web Vitals¶

graph LR
    A[LCP<br/>Largest Contentful Paint] --> D[User Experience]
    B[FID<br/>First Input Delay] --> D
    C[CLS<br/>Cumulative Layout Shift] --> D
    D --> E[SEO Ranking]

Metric	Good	Needs Improvement	Poor
LCP	≤2.5s	≤4.0s	>4.0s
FID	≤100ms	≤300ms	>300ms
CLS	≤0.1	≤0.25	>0.25

Performance Auditing¶

1. Run Comprehensive Audit¶

// AI Command:
"Run full Lighthouse performance audit"

// Returns:
- Performance score (0-100)
- Core Web Vitals
- Opportunities for improvement
- Diagnostics
- Passed audits

2. Specific Performance Checks¶

// AI Commands:
"Check First Contentful Paint time"
"Analyze JavaScript execution time"
"Find render-blocking resources"
"Measure Time to Interactive"
"Check Total Blocking Time"

3. Resource Analysis¶

// AI Commands:
"List largest JavaScript bundles"
"Find unoptimized images"
"Check for unused CSS"
"Analyze third-party script impact"

Performance Optimization Strategies¶

1. JavaScript Optimization¶

Bundle Size Reduction¶

// Before: Large bundle
import moment from 'moment'; // 67KB
import _ from 'lodash'; // 71KB

// After: Tree-shaking and alternatives
import { format } from 'date-fns'; // 2KB
import debounce from 'lodash/debounce'; // 1KB

Code Splitting¶

// Lazy load routes
const Dashboard = lazy(() => import('./Dashboard'));

// Lazy load heavy components
const Chart = lazy(() => import('./Chart'));

// Conditional loading
if (user.needsAnalytics) {
  import('./analytics').then(module => {
    module.init();
  });
}

Performance Monitoring¶

// AI Commands for JS performance:
"Identify long-running scripts"
"Find JavaScript memory leaks"
"Check for excessive DOM manipulation"
"Analyze React re-renders"

2. Image Optimization¶

Modern Format Usage¶

<!-- Before: Large JPEG -->
<img src="hero.jpg" /> <!-- 500KB -->

<!-- After: Modern formats with fallback -->
<picture>
  <source srcset="hero.avif" type="image/avif" /> <!-- 150KB -->
  <source srcset="hero.webp" type="image/webp" /> <!-- 200KB -->
  <img src="hero.jpg" alt="Hero" /> <!-- Fallback -->
</picture>

Lazy Loading¶

<!-- Native lazy loading -->
<img src="image.jpg" loading="lazy" alt="Description" />

<!-- Intersection Observer for advanced control -->
<script>
const images = document.querySelectorAll('[data-src]');
const imageObserver = new IntersectionObserver((entries) => {
  entries.forEach(entry => {
    if (entry.isIntersecting) {
      entry.target.src = entry.target.dataset.src;
      imageObserver.unobserve(entry.target);
    }
  });
});
images.forEach(img => imageObserver.observe(img));
</script>

AI Commands for Images¶

"Find images without proper sizing"
"Check for missing image dimensions"
"List images over 100KB"
"Analyze image format usage"

3. CSS Optimization¶

Critical CSS¶

<!-- Inline critical CSS -->
<style>
  /* Above-the-fold styles */
  .hero { background: #000; height: 100vh; }
  .nav { position: fixed; top: 0; }
</style>

<!-- Lazy load non-critical CSS -->
<link rel="preload" href="styles.css" as="style" onload="this.onload=null;this.rel='stylesheet'">

Remove Unused CSS¶

// PurgeCSS configuration
module.exports = {
  content: ['./src/**/*.{js,jsx,ts,tsx}'],
  css: ['./src/**/*.css'],
  safelist: ['dynamic-class', /^modal-/]
};

AI Commands for CSS¶

"Find unused CSS rules"
"Check CSS file sizes"
"Identify render-blocking stylesheets"
"Analyze CSS complexity"

4. Network Optimization¶

Resource Hints¶

<!-- DNS Prefetch -->
<link rel="dns-prefetch" href="//api.example.com">

<!-- Preconnect -->
<link rel="preconnect" href="https://fonts.googleapis.com">

<!-- Prefetch -->
<link rel="prefetch" href="/next-page.html">

<!-- Preload -->
<link rel="preload" href="/font.woff2" as="font" crossorigin>

Caching Strategy¶

// Service Worker caching
self.addEventListener('fetch', (event) => {
  event.respondWith(
    caches.match(event.request).then((response) => {
      return response || fetch(event.request).then((response) => {
        return caches.open('v1').then((cache) => {
          cache.put(event.request, response.clone());
          return response;
        });
      });
    })
  );
});

AI Commands for Network¶

"Analyze cache hit rates"
"Find resources without caching headers"
"Check for redundant requests"
"Monitor WebSocket performance"

Performance Monitoring¶

1. Real User Monitoring (RUM)¶

// Collect performance metrics
const perfData = {
  lcp: 0,
  fid: 0,
  cls: 0
};

// Largest Contentful Paint
new PerformanceObserver((list) => {
  const entries = list.getEntries();
  const lastEntry = entries[entries.length - 1];
  perfData.lcp = lastEntry.renderTime || lastEntry.loadTime;
}).observe({ type: 'largest-contentful-paint', buffered: true });

// First Input Delay
new PerformanceObserver((list) => {
  const entries = list.getEntries();
  entries.forEach((entry) => {
    perfData.fid = entry.processingStart - entry.startTime;
  });
}).observe({ type: 'first-input', buffered: true });

// Cumulative Layout Shift
new PerformanceObserver((list) => {
  let cls = 0;
  list.getEntries().forEach((entry) => {
    if (!entry.hadRecentInput) {
      cls += entry.value;
    }
  });
  perfData.cls = cls;
}).observe({ type: 'layout-shift', buffered: true });

2. Synthetic Monitoring¶

// AI Commands for monitoring:
"Set up performance monitoring"
"Track Core Web Vitals over time"
"Alert on performance regression"
"Compare performance across deployments"

3. Performance Budgets¶

// webpack.config.js
module.exports = {
  performance: {
    maxAssetSize: 244000, // 244KB
    maxEntrypointSize: 244000,
    hints: 'error',
    assetFilter: (assetFilename) => {
      return !assetFilename.endsWith('.map');
    }
  }
};

Framework-Specific Optimizations¶

React Performance¶

// 1. Memoization
const ExpensiveComponent = memo(({ data }) => {
  return <div>{/* Complex rendering */}</div>;
});

// 2. useMemo for expensive computations
const filteredData = useMemo(() => {
  return data.filter(item => item.active);
}, [data]);

// 3. useCallback for function stability
const handleClick = useCallback(() => {
  // Handle click
}, [dependency]);

// 4. Virtual scrolling for long lists
import { FixedSizeList } from 'react-window';

const List = ({ items }) => (
  <FixedSizeList
    height={600}
    itemCount={items.length}
    itemSize={50}
    width="100%"
  >
    {({ index, style }) => (
      <div style={style}>{items[index]}</div>
    )}
  </FixedSizeList>
);

Vue Performance¶

// 1. Lazy loading components
const UserProfile = () => import('./UserProfile.vue');

// 2. Keep-alive for component caching
<keep-alive>
  <component :is="currentComponent" />
</keep-alive>

// 3. v-once for static content
<div v-once>
  {{ staticContent }}
</div>

// 4. Computed properties for derived state
computed: {
  filteredList() {
    return this.items.filter(item => item.active);
  }
}

Angular Performance¶

// 1. OnPush change detection
@Component({
  changeDetection: ChangeDetectionStrategy.OnPush
})

// 2. TrackBy for lists
trackByFn(index: number, item: any) {
  return item.id;
}

// 3. Lazy loading modules
const routes: Routes = [
  {
    path: 'admin',
    loadChildren: () => import('./admin/admin.module').then(m => m.AdminModule)
  }
];

// 4. Pure pipes for transformations
@Pipe({ name: 'filter', pure: true })

Performance Testing¶

1. Load Testing¶

// AI Commands:
"Simulate 100 concurrent users"
"Test performance under heavy load"
"Find breaking point of the application"
"Measure response times under stress"

2. Performance Regression Testing¶

// CI/CD Integration
{
  "scripts": {
    "perf:test": "lighthouse https://staging.example.com --output json --output-path ./lighthouse.json",
    "perf:assert": "node assert-performance.js"
  }
}

// assert-performance.js
const results = require('./lighthouse.json');
const { performance } = results.categories;

if (performance.score < 0.9) {
  console.error(`Performance score ${performance.score} is below threshold`);
  process.exit(1);
}

3. A/B Testing Performance¶

// Compare performance of different implementations
"Compare performance of old vs new checkout flow"
"Measure impact of lazy loading on LCP"
"Test performance with and without service worker"

Performance Debugging¶

Common Performance Issues¶

1. Slow Initial Load¶

// Debugging steps:
"Check bundle size and splitting"
"Analyze critical rendering path"
"Find render-blocking resources"
"Check server response time"

// Solutions:
- Code splitting
- Preloading critical resources
- CDN implementation
- Server-side rendering

2. Janky Scrolling¶

// Debugging steps:
"Profile scrolling performance"
"Check for layout thrashing"
"Find expensive paint operations"
"Analyze composite layers"

// Solutions:
- Use CSS transforms
- Implement virtual scrolling
- Debounce scroll handlers
- Use will-change property

3. Memory Leaks¶

// Debugging steps:
"Monitor memory usage over time"
"Check for detached DOM nodes"
"Find event listener leaks"
"Analyze closure retention"

// Solutions:
- Remove event listeners
- Clear timers and intervals
- Weak references for caches
- Proper component cleanup

Performance Optimization Workflow¶

Step-by-Step Process¶

graph TD
    A[Baseline Measurement] --> B[Identify Bottlenecks]
    B --> C[Prioritize Issues]
    C --> D[Implement Fixes]
    D --> E[Measure Impact]
    E --> F{Goal Met?}
    F -->|No| B
    F -->|Yes| G[Monitor & Maintain]

AI-Assisted Workflow¶

// 1. Initial audit
"Run comprehensive performance audit"

// 2. Analysis
"What are the top 3 performance issues?"

// 3. Solutions
"How can I improve Largest Contentful Paint?"

// 4. Implementation
"Help me implement lazy loading for images"

// 5. Verification
"Measure performance improvement after changes"

Performance Checklist¶

Pre-Launch Checklist¶

Images optimized - WebP/AVIF, proper sizing, lazy loading
JavaScript bundled - Code splitting, tree shaking, minification
CSS optimized - Critical CSS inlined, unused CSS removed
Fonts optimized - Subset, preload, font-display: swap
Caching configured - Browser cache, CDN, service worker
Compression enabled - Gzip/Brotli for text assets
HTTP/2 enabled - Multiplexing, server push
Performance budget set - Size limits, metric thresholds

Monitoring Checklist¶

RUM implemented - Real user metrics collection
Alerts configured - Performance regression alerts
Regular audits - Weekly/monthly Lighthouse runs
A/B testing - Performance impact measurement
Competitive analysis - Benchmark against competitors

Advanced Topics¶

1. Web Workers¶

// Offload heavy computations
const worker = new Worker('worker.js');

worker.postMessage({ cmd: 'process', data: largeDataset });

worker.onmessage = (e) => {
  console.log('Processing complete:', e.data);
};

// worker.js
self.onmessage = (e) => {
  if (e.data.cmd === 'process') {
    const result = expensiveOperation(e.data.data);
    self.postMessage(result);
  }
};

2. WebAssembly¶

// High-performance computations
WebAssembly.instantiateStreaming(fetch('compute.wasm'))
  .then(result => {
    const compute = result.instance.exports.compute;
    const result = compute(data);
  });

3. Edge Computing¶

// Cloudflare Workers example
addEventListener('fetch', event => {
  event.respondWith(handleRequest(event.request));
});

async function handleRequest(request) {
  // Cache at edge
  const cache = caches.default;
  const cached = await cache.match(request);

  if (cached) {
    return cached;
  }

  const response = await fetch(request);
  event.waitUntil(cache.put(request, response.clone()));

  return response;
}

Tools and Resources¶

Performance Tools¶

Lighthouse - Comprehensive auditing
WebPageTest - Detailed performance testing
Chrome DevTools - Performance profiling
GTmetrix - Performance monitoring
Calibre - Performance tracking

AI Commands Reference¶

// Quick performance checks
"performance" - Run basic audit
"slow" - Find slow elements
"optimize" - Get optimization suggestions

// Detailed analysis
"audit performance with focus on mobile"
"compare performance before and after deployment"
"track performance metrics for the last hour"

// Specific optimizations
"optimize images on this page"
"reduce JavaScript bundle size"
"improve Time to Interactive"

Next Steps¶

🔍 Debugging Guide - Debug performance issues
🔒 Security Guide - Secure optimizations
🚀 IDE Integration - Set up tools
📊 API Reference - Performance APIs

Support¶

Need performance help?