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