How does useMemo optimize performance?

Short answer: useMemo memoizes a computed value to avoid recalculating unless dependencies change. ✅ Syntax: const memoizedValue = useMemo(() => computeExpensiveValue(a, b), [a, b]); ✅ Use case: Avoid recalculating heavy logic on every render. const filteredList = useMemo(() => { return items.filter(item => item.includes(searchTerm)); }, [items, searchTerm]);

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.