performance-regression-debugging

SKILL.md

Performance Regression Debugging

Table of Contents

Overview

When to Use

Quick Start

Reference Guides

Best Practices

Overview

Performance regressions occur when code changes degrade application performance. Detection and quick resolution are critical.

When to Use

After deployment performance degrades

Metrics show negative trend

User complaints about slowness

A/B testing shows variance

Regular performance monitoring

Quick Start

Minimal working example:

// Before: 500ms response time
// After: 1000ms response time (2x slower = regression)

// Capture baseline metrics
const baseline = {
  responseTime: 500, // ms
  timeToInteractive: 2000, // ms
  largestContentfulPaint: 1500, // ms
  memoryUsage: 50, // MB
  bundleSize: 150, // KB gzipped
};

// Monitor after change
const current = {
  responseTime: 1000,
  timeToInteractive: 4000,
  largestContentfulPaint: 3000,
  memoryUsage: 150,
  bundleSize: 200,
};

// Calculate regression
const regressions = {};
for (let metric in baseline) {
  const change = (current[metric] - baseline[metric]) / baseline[metric];
// ... (see reference guides for full implementation)

Reference Guides

Detailed implementations in the references/ directory:

Guide
Contents

Detection & Measurement
Detection & Measurement

Root Cause Identification
Root Cause Identification

Fixing & Verification
Fixing & Verification

Prevention Measures
Prevention Measures

Best Practices

✅ DO

Follow established patterns and conventions

Write clean, maintainable code

Add appropriate documentation

Test thoroughly before deploying

❌ DON'T

Skip testing or validation

Ignore error handling

Hard-code configuration values

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