Agent skill

performance-profiling

Identify performance bottlenecks systematically. Measure before optimizing.

View SKILL.md on GitHub Repository
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Install this agent skill to your Project

npx add-skill https://github.com/timequity/vibe-coder/tree/main/skills/performance-profiling

SKILL.md

Performance Profiling

Core Principle

Measure first. Optimize second. Verify third.

Never optimize based on intuition. Profile to find actual bottlenecks.

The Process

1. Establish Baseline

bash
# Node.js
node --prof app.js
node --prof-process isolate-*.log > profile.txt

# Browser
Performance tab → Record → Analyze

2. Identify Bottlenecks

Look for:

  • Functions with high "self time"
  • Unexpected call counts
  • Memory allocations in hot paths
  • N+1 queries

3. Form Hypothesis

"Function X is slow because Y"

4. Optimize Minimally

One change at a time:

  • Caching
  • Algorithm improvement
  • Batch operations
  • Lazy loading

5. Verify Improvement

Compare against baseline. Must be measurably better.

Common Bottlenecks

Symptom Likely Cause
Slow page load Large bundle, blocking resources
Slow API N+1 queries, missing indexes
Memory growth Leaks, unbounded caches
CPU spikes Inefficient loops, regex

Tools

Node.js:

  • --prof flag
  • clinic.js
  • 0x flame graphs

Browser:

  • DevTools Performance
  • Lighthouse
  • WebPageTest

Database:

  • EXPLAIN ANALYZE
  • Query logs
  • Connection pool stats

Red Flags

  • Optimizing without profiling
  • "I think this is slow"
  • Premature optimization
  • Micro-optimizations in cold paths

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