“More memoization = more performance.”

useMemo and useCallback trade CPU and memory for the chance to skip work later. That trade pays off only when three things are true: the skipped work is expensive, the dependencies genuinely stay stable, and the consumer can actually bail out.

1// The child is not memoised, so it re-renders anyway.2// All this adds is a comparison and a retained closure.3const onClick = useCallback(() => setOpen(true), []);4return <Button onClick={onClick} />;

Memoisation also keeps values alive. A useMemo holding a large derived array retains it for the lifetime of the component, which is the desired behaviour when it is expensive to recompute, and a leak when it is not.

The React Compiler changes the economics: it inserts memoisation automatically where it can prove the component is pure, which removes both the manual effort and the class of bugs caused by wrong dependency arrays.