Performance Patterns

1) Keep selectors fine-grained

Prefer s => s.items[i].value over selecting a large object. Smaller selections → fewer renders.

const value = useStoreSelector(store, s => s.items[i].value);

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2) Structural sharing

When updating arrays/objects, clone only the changed layer.

store.setState(p => {
  const items = p.items.slice();
  items[i] = { ...items[i], value: items[i].value + 1 };
  return { ...p, items };
});

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3) Avoid expensive equals

Default Object.is is fast. If you pass a custom equality, keep it cheap and shallow.

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4) Measure

Use React Profiler in production build.
You can also count re-renders with a useEffect bump while benchmarking.

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5) When to reach for something bigger

If you need cross-app caching, middleware stacks, or normalized entity graphs, combine this library with a dedicated data layer.
For many UI flows, selector-first local stores are faster & simpler.