performance-profiler

---
name: performance-profiler
description: Use when investigating slow endpoints, planning performance budgets, or hunting memory leaks in production applications.
category: Engineering
version: 1.0.0
tools: []
---

# Performance Profiler

**Tier:** POWERFUL  
**Domain:** Performance Engineering

Systematic performance profiling for Node.js, Python, and Go applications. Identifies CPU, memory, and I/O bottlenecks; generates flamegraphs; analyzes bundle sizes; optimizes database queries; detects memory leaks; and runs load tests.

## Core Capabilities

- **CPU profiling** — flamegraphs for Node.js, py-spy for Python, pprof for Go
- **Memory profiling** — heap snapshots, leak detection, GC pressure
- **Bundle analysis** — webpack-bundle-analyzer, Next.js bundle analyzer
- **Database optimization** — EXPLAIN ANALYZE, slow query log, N+1 detection
- **Load testing** — k6 scripts, Artillery scenarios, ramp-up patterns
- **Before/after measurement** — establish baseline, profile, optimize, verify

## When to Use

- App is slow; bottleneck is unknown
- P99 latency exceeds SLA before release
- Memory usage grows over time (suspected leak)
- Bundle size increased after adding dependencies
- Preparing for traffic spike (load test before launch)
- Database queries taking >100ms

## Golden Rule: Measure First

Establish baseline BEFORE optimization:
- Record P50, P95, P99 latency
- Record RPS, error rate, memory usage
- Profile → confirm bottleneck → fix → measure again → verify improvement

## Node.js Profiling Workflow

Use Node.js Inspector for CPU and heap snapshots:
- CPU: `node --prof`, then `node --prof-process` for flamegraph
- Memory: heap snapshots via DevTools
- Streaming: use clinic.js or 0x for real-time flamegraphs

## Database Optimization

- Run `EXPLAIN ANALYZE` on slow queries
- Add indexes on frequently filtered columns
- Detect N+1 queries via query logging
- Use connection pooling

## Load Testing

- k6 for scripted load tests with realistic user flows
- Artillery for simpler, declarative scenarios
- Ramp up gradually; measure P50/P95/P99 latency under load
- Target: maintain SLA under peak traffic

## Bundle Analysis

- webpack-bundle-analyzer for JS/CSS sizes
- Next.js built-in analyzer for app router
- Identify unused dependencies
- Set bundle size budgets in CI