Performance Optimization

Performance Optimization Skill

Optimization Principles

1. Measure First

Never optimize without profiling data.

2. Focus on Bottlenecks

Optimize the slowest 20%, not everything.

3. Maintain Readability

Performance gains shouldn't sacrifice clarity.

4. Test After Changes

Verify optimizations don't break functionality.

Common Bottlenecks

Database

• N+1 queries
• Missing indexes
• Unoptimized queries
• Connection pool exhaustion

Network

• Too many requests
• Large payloads
• Missing caching
• Slow DNS resolution

CPU

• Inefficient algorithms
• Unnecessary computation
• Blocking operations
• Poor parallelization

Memory

• Memory leaks
• Large objects in memory
• Unnecessary copies
• Missing garbage collection

Profiling Tools

JavaScript/Node.js

# CPU profiling
node --prof app.js
node --prof-process isolate-*.log

# Memory profiling
node --inspect app.js
# Open chrome://inspect

# Benchmark
npm install -g autocannon
autocannon -c 100 -d 30 http://localhost:3000

Database

-- PostgreSQL
EXPLAIN ANALYZE SELECT * FROM users WHERE email = 'test@example.com';

-- Add index
CREATE INDEX idx_users_email ON users(email);

Optimization Patterns

Caching

const cache = new Map();

async function getData(id: string) {
  if (cache.has(id)) {
    return cache.get(id);
  }
  const data = await fetchData(id);
  cache.set(id, data);
  return data;
}

Batching

// Instead of N individual queries
const users = await Promise.all(ids.map(id => getUser(id)));

// Use batch query
const users = await getUsersByIds(ids);

Lazy Loading

// Load only when needed
const heavyModule = await import('./heavy-module');

Pagination

// Instead of loading all
const users = await db.users.findMany({
  skip: page * pageSize,
  take: pageSize,
});

Performance Checklist

Frontend

• Bundle size optimized
• Images optimized
• Code splitting implemented
• Lazy loading for heavy components
• Caching headers set

Backend

• Database queries optimized
• Proper indexes in place
• Caching implemented
• Connection pooling configured
• Async operations used

Infrastructure

• CDN configured
• Compression enabled
• HTTP/2 enabled
• Geographic distribution

Metrics to Track

Performance Report

# Performance Analysis

**Date:** {YYYY-MM-DD}
**Scope:** {What was analyzed}

## Current Performance
{Baseline metrics}

## Bottlenecks Identified
1. {Bottleneck 1} - {Impact}
2. {Bottleneck 2} - {Impact}

## Optimizations Applied
1. {Change 1} - {Improvement}
2. {Change 2} - {Improvement}

## Results
{Before/after comparison}

## Recommendations
{Future improvements}

Best Practices

1. Profile regularly - Not just when slow
2. Set budgets - Performance budgets for key metrics
3. Monitor production - Lab != production
4. Automate testing - CI performance tests
5. Document baselines - Track trends over time

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