Eaton

CAW Studios

🔹 Round 1 – React Core, Rendering, Performance

React Internals

  1. How does React reconciliation work under the hood?

  2. What triggers a re-render even when state hasn’t changed?

  3. Explain the difference between Virtual DOM vs Fiber DOM.

  4. What changed in concurrent rendering under React 18/19?

Hooks & State

  1. Why does useEffect run twice in Strict Mode?

  2. Difference between useCallback and useMemo.

  3. How does useTransition help in avoiding UI blocking?

  4. When should you use useRef over state?

Performance

  1. What causes hydration errors in SSR/Next?

  2. Lazy vs Suspense vs dynamic imports – when to use what?

  3. How does React bundle splitting actually reduce TTI?

Advanced Patterns

  1. Controlled vs uncontrolled components