Frontend performance optimization strategies - loading, rendering, and runtime performance

Performance Optimization

Performance directly impacts user experience, SEO, and business metrics. This section covers comprehensive strategies for optimizing frontend applications.

Core Topics

Loading Performance

Bundle optimization, lazy loading, caching

Rendering Performance

DOM optimization, reflow, repaint

Code Optimization

Algorithm efficiency, memory management

Monitoring

Metrics, tools, and performance budgets

Core Web Vitals

Google's Core Web Vitals are essential metrics for measuring user experience.

Metric	Description	Good	Needs Improvement	Poor
LCP	Largest Contentful Paint	≤2.5s	2.5s-4s	>4s
INP	Interaction to Next Paint	≤200ms	200ms-500ms	>500ms
CLS	Cumulative Layout Shift	≤0.1	0.1-0.25	>0.25

Performance Budget Example

{
  "timings": {
    "firstContentfulPaint": 1500,
    "largestContentfulPaint": 2500,
    "interactive": 3500,
    "totalBlockingTime": 300
  },
  "sizes": {
    "javascript": 300000,
    "css": 50000,
    "images": 500000,
    "fonts": 100000,
    "total": 1000000
  },
  "requests": {
    "javascript": 10,
    "css": 3,
    "images": 20,
    "fonts": 4,
    "total": 50
  }
}

Optimization Workflow

Performance Optimization Cycle
├── Measure
│   ├── Lighthouse audit
│   ├── Core Web Vitals
│   └── Real User Monitoring
├── Analyze
│   ├── Identify bottlenecks
│   ├── Prioritize by impact
│   └── Set improvement targets
├── Optimize
│   ├── Implement changes
│   ├── A/B test if needed
│   └── Document improvements
└── Monitor
    ├── Track metrics over time
    ├── Alert on regressions
    └── Continuous improvement