RTK Query and React Query look identical from the outside.

RTK Query and React Query look identical from the outside.

Both cache API responses.
Both deduplicate in-flight requests.
Both have cache invalidation.
Both give you loading/error states.

So developers ask: which one should I use?

Wrong question. The right question is: where do you believe server state belongs?

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RTK Query's architectural answer:

Server state is just another slice of your Redux store.

The cache lives inside Redux. That means:
→ Your API responses are inspectable in Redux DevTools
→ Your server state and client state share the same update cycle
→ Cache invalidation is a Redux action under the hood
→ You can select server cache the same way you select any Redux state

RTK Query treats the server as an external mutation source — but the data, once fetched, becomes Redux state. You own it now.

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React Query's architectural answer:

Server state doesn't belong in your state manager at all.

The cache is completely isolated — React Query has no idea Redux exists, and Redux has no idea React Query exists. They operate in different layers entirely.

React Query treats every cached value as a temporary observation. It never fully trusts local state. staleTime is not an optimization — it's a philosophical statement: "I don't own this truth, I'm just borrowing it."

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One layer deeper — the invalidation model:

RTK Query invalidation: tag-based.
You define tags on queries and mutations. When a mutation runs, it invalidates matching tags. Deterministic. Explicit. You're in control.

React Query invalidation: time + intent based.
Data goes stale automatically after staleTime. You also manually call queryClient.invalidateQueries(). The cache itself knows it might be wrong — you don't have to tell it.

RTK Query: "invalid until I say otherwise"
React Query: "valid until time proves otherwise"

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So which one?

If your app is Redux-first and server state needs to be part of a unified state model → RTK Query. The integration is seamless and DevTools alone are worth it.

If server state is its own concern — separate from UI state, separate from client decisions → React Query. The isolation is a feature, not a limitation.

The confusion happens because both solve the same surface problem.
The difference is where they believe the truth should live.

Redux says: truth lives in the store.
React Query says: truth lives on the server. We just cache it.