Performance Checklist
Overview
Use this checklist to catch common performance problems before they hurt users.
Why It Matters
Performance issues are easier to prevent than to diagnose in production.
Core Concepts
- Measure first.
- Optimize the bottleneck.
- Verify on realistic conditions.
Mental Models
Speed is often limited by the slowest visible step in the user journey.
Best Practices
- Check bundle size and render cost.
- Test slow network and slow device cases.
- Prefer perceived speed improvements when they help.
Common Mistakes
- Premature memoization.
- Optimizing things users never notice.
- Ignoring slow initial load or repeated re-rendering.
Trade-offs
Performance work can complicate code, so it should be driven by actual user pain or measured bottlenecks.
Decision Framework
| Symptom | Check |
|---|---|
| Slow load | Network and bundle size |
| Janky UI | Render and main thread work |
| Slow interaction | State updates and re-renders |
Examples
- Measure before adding memoization.
Checklists
- Did I measure the slowdown?
- Is the fix user-visible?
- Did I verify the result?
Senior Engineer Notes
Senior engineers optimize carefully and only where it pays back. The goal is a faster user experience, not more clever code.