How does useMemo optimize performance?

Short answer: void recalculating heavy logic on every render.

Explain a bit more

const filteredList = useMemo(() => { return items.filter(item => item.includes(searchTerm)); }, [items, searchTerm]); void recalculating heavy logic on every render. const filteredList = useMemo(() => { return items.filter(item => item.includes(searchTerm)); }, [items, searchTerm]); void recalculating heavy logic on every render. const filteredList = useMemo(() => { return items.filter(item => item.includes(searchTerm)); }, [items, searchTerm]); void recalculating heavy logic on every render. const filteredList = useMemo(() => { return items.filter(item => item.includes(searchTerm)); }, [items, searchTerm]);

Real-world example (ShopNest)

Heavy product grids memoize row components so typing in the search box does not re-render every image card unnecessarily.

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.