# When You Need a Store — Redux Toolkit / Zustand

Source: https://www.skillbyai.com/en/redux-zustand/f-when

> And when React state, Context or a server cache is better.

## Signals that a store helps

A global store pays off when many components far apart in the tree read and update the same client-owned data, when updates follow non-trivial rules you want to keep in one place, when you want to inspect or replay changes in DevTools, or when logic must run outside components. It is usually **not** needed for data that comes from an API: a server-cache library such as **TanStack Query** or **RTK Query** handles fetching, caching and refetching better than hand-written reducers. React **Context** is fine for values that change rarely (theme, locale, the current user object) but every consumer re-renders when the context value changes.

## A decision sketch

Rules of thumb, not laws.

```text
used by one component or a small subtree        -> useState / useReducer
changes rarely, read in many places (theme)      -> React Context
fetched from a server, needs caching/refetching  -> TanStack Query or RTK Query
client-owned, shared widely, updated often       -> Zustand or Redux Toolkit
complex rules, many contributors, DevTools/time travel valued -> Redux Toolkit
```

## A notice board versus sticky notes

Sticky notes on your own desk are local state. A shared notice board in the hallway is a store: worth having when many people need the same information, overkill for a personal reminder.

**Quiz:** For data fetched from a REST API with caching and refetch needs, what is usually the best fit?

- [x] A server-cache library such as TanStack Query or RTK Query
- [ ] A hand-written Redux reducer for every endpoint
- [ ] React Context with useState
- [ ] localStorage

*Answer:* A server-cache library such as TanStack Query or RTK Query. Server-cache libraries handle loading flags, deduplication, staleness and invalidation for you.