React Best Practices

Overview

Performance optimization guide for React and Next.js applications, ordered by impact. Apply these patterns when writing or reviewing code to maximize performance gains.

When to Apply

Reference these guidelines when:

• Writing new React components or Next.js pages
• Implementing data fetching (client or server-side)
• Reviewing code for performance issues
• Refactoring existing React/Next.js code
• Optimizing bundle size or load times

Priority-Ordered Guidelines

Rules are prioritized by impact:

Priority	Category	Impact
1	Eliminating Waterfalls	CRITICAL
2	Bundle Size Optimization	CRITICAL
3	Server-Side Performance	HIGH
4	Client-Side Data Fetching	MEDIUM-HIGH
5	Re-render Optimization	MEDIUM
6	Rendering Performance	MEDIUM
7	JavaScript Performance	LOW-MEDIUM
8	Advanced Patterns	LOW

Quick Reference

Critical Patterns (Apply First)

Eliminate Waterfalls:

• Use Promise.all() for independent async operations
• Start promises early, await late
• Use better-all for partial dependencies
• Use Suspense boundaries to stream content

Reduce Bundle Size:

• Avoid barrel file imports (import directly from source)
• Use next/dynamic for heavy components
• Defer non-critical third-party libraries
• Preload based on user intent

High-Impact Server Patterns

• Use React.cache() for per-request deduplication
• Use LRU cache for cross-request caching
• Minimize serialization at RSC boundaries
• Parallelize data fetching with component composition

Medium-Impact Client Patterns

• Use SWR for automatic request deduplication
• Defer state reads to usage point
• Use derived state subscriptions
• Apply startTransition for non-urgent updates

References

Full documentation with code examples is available in:

• references/react-performance-guidelines.md - Complete guide with all patterns
• references/rules/ - Individual rule files organized by category

To look up a specific pattern, grep the rules directory:

grep -l "suspense" references/rules/
grep -l "barrel" references/rules/
grep -l "swr" references/rules/

Rule Categories in references/rules/

• async-* - Waterfall elimination patterns
• bundle-* - Bundle size optimization
• server-* - Server-side performance
• client-* - Client-side data fetching
• rerender-* - Re-render optimization
• rendering-* - DOM rendering performance
• js-* - JavaScript micro-optimizations
• advanced-* - Advanced patterns