React Patterns

Performance and composition patterns for React 19 + Vite + Cloudflare Workers projects. Use as a checklist when writing new components, a review guide when auditing existing code, or a refactoring playbook when something feels slow or tangled.

Rules are ranked by impact. Fix CRITICAL issues before touching MEDIUM ones.

When to Apply

• Writing new React components or pages
• Reviewing code for performance issues
• Refactoring components with too many props or re-renders
• Debugging "why is this slow?" or "why does this re-render?"
• Building reusable component libraries
• Code review before merging

1. Eliminating Waterfalls (CRITICAL)

Sequential async calls where they could be parallel. The #1 performance killer.