Agent Skills: React Performance

React Performance

Priority: P0 (CRITICAL)

Strategies to minimize waterfalls, bundle size, and render cost.

Eliminate Data Waterfalls (P0)

• Parallel Data: Use Promise.all([getUser(), getProducts(), ...]) for independent fetches. Avoid sequential awaits (Request Waterfalls).
• Preload: Start fetches before render (in event handlers or route loaders).
• Suspense: Use Suspense boundaries to stream partial content and show partial content early.

See implementation examples for parallel fetch with Suspense boundary and lazy loading patterns.

Reduce Bundle Size (P0)

• No Barrel Files: Avoid barrel files (importing from index.ts); import directly from component files to improve tree-shaking.
• Lazy Load: Use React.lazy or next/dynamic for heavy components like Charts, Modals, or large libraries.
• Dependency Reduction: Replace moment with dayjs or lodash with native/radash to drop bytes. Use source-map-explorer or bundle-visualizer to find bloat.

Minimize Re-renders (P1)

• Isolation: Move state as close to its usage as possible. Isolate heavy UI updates.
• List Performance: Use react-window or react-virtual for virtualization of lists with 500+ items. Wrap list items in React.memo.
• Context Splitting: Split Context into State and Dispatch objects. This prevents all consumers from re-rendering when only a setter is needed.
• Stability: Use useMemo for derived list data and passing stable object/array references to children.
• Content Visibility: content-visibility: auto for off-screen CSS content.
• Static Hoisting: Extract static objects/JSX outside component scope.
• Transitions: startTransition for non-urgent UI updates.

Parallelize Computation (P1)

• Web Workers: Move heavy computation (Encryption, Image processing, Large Data Sorting) off the main thread using Comlink or Worker.

Optimize Server Components (RSC) (P1)

• Caching: React.cache for per-request deduplication.
• Serialization: Minimize props passing to Client Components (only IDs/primitives).

Anti-Patterns

• No export *: Breaks tree-shaking.
• No Sequential Await: Causes waterfalls.
• No Inline Objects: style={{}} breaks strict equality checks (if memoized).
• No Heavy Libs: Avoid moment/lodash (use dayjs/radash).

References

See references/REFERENCE.md for Profiler usage, bundle analysis, Web Workers, and debounce patterns.