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name: performance-optimizer description: "Identify and resolve performance bottlenecks through profiling, measurement, and targeted optimization." autoInvoke: false priority: medium triggers:

• "performance optimization"
• "slow"
• "bottleneck"

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Skill: Performance Optimizer

Category: Dev Expert Version: 1.0.0 Used By: All development agents

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Overview

Identify and resolve performance bottlenecks through profiling, measurement, and targeted optimization.

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1. Performance Optimization Rules

Copy1. Measure first, optimize second
2. Optimize the bottleneck, not everything
3. 80/20 rule: 80% of slowness is in 20% of code
4. Premature optimization is the root of all evil

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2. Profiling Strategy

When to Profile

• Before optimization (baseline)
• After each change (verify improvement)
• Production (real user data)

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3. Frontend Optimization

Core Web Vitals Targets

Quick Wins

Copy// Lazy load images
<img loading="lazy" src="image.jpg" />

// Code splitting
const Component = lazy(() => import('./Component'))

// Debounce handlers
const handleSearch = debounce((q) => search(q), 300)

// Memoize expensive computations
const result = useMemo(() => expensiveCalc(data), [data])

Checklist

• Images optimized (WebP, lazy loading)
• Code split by route
• CSS/JS minified and compressed
• Caching headers set
• Fonts preloaded

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4. Backend Optimization

Common Bottlenecks

Quick Wins

Copy// Batch database calls
const users = await User.findByIds(ids)  // 1 query, not N

// Add indexes
CREATE INDEX idx_users_email ON users(email)

// Cache expensive queries
const data = await cache.getOrSet('key', () => db.query(), 3600)

// Parallel async
const [users, orders] = await Promise.all([getUsers(), getOrders()])

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5. Database Optimization

Query Analysis

Copy-- Always EXPLAIN slow queries
EXPLAIN ANALYZE SELECT * FROM orders WHERE user_id = 123;

-- Look for: Seq Scan (bad), Index Scan (good)

Index Strategy

Checklist

• Indexes on WHERE/JOIN columns
• No SELECT * (specify columns)
• Pagination on large tables
• Connection pooling enabled
• Query result caching

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6. Caching Strategy

Cache Invalidation

Copy// Time-based
cache.set(key, value, { ttl: 3600 })

// Event-based
onUserUpdate(user => cache.delete(`user:${user.id}`))

// Version-based
cache.set(`data:v${version}`, value)

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7. Memory Optimization

Common Leaks

Detection

Copy// Node.js heap snapshot
const v8 = require('v8')
v8.writeHeapSnapshot()

// Browser DevTools
// Memory tab → Take heap snapshot → Compare

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8. Optimization Checklist

Before:

• Baseline metrics captured
• Bottleneck identified via profiling
• Target improvement defined

After:

• Metrics improved
• No regressions introduced
• Tests still pass

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Best Practices

Do's

• Measure before and after
• Optimize biggest bottleneck first
• Use appropriate data structures
• Cache strategically
• Profile in production-like env

Don'ts

• Optimize without measuring
• Micro-optimize everything
• Cache without invalidation strategy
• Ignore memory leaks
• Sacrifice readability for speed

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Version: 1.0.0 | Last Updated: 2025-11-28