React Performance: Advanced — useLatest Hook. Keywords: uselatest ref callback. Platform: React/Next.js. Description: Access latest values in callbacks without adding to dependency arrays. Do: Use useLatest for fresh values in stable callbacks. Don't: Add callback to effect dependencies. Good Example: const cbRef = useLatest(cb); useEffect(() => { setTimeout(() => cbRef.current()) }, []). Bad Example: useEffect(() => { setTimeout(() => cb()) }, [cb]) // re-runs. Severity: Low.