Questions
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11. How do you structure Redux Toolkit in a large-scale React app (folder structure)?
22. How would you migrate an old Redux app to Redux Toolkit?
33. How do you integrate RTK Query and createAsyncThunk in the same app?
44. How do you persist Redux state across reloads while using RTK Query?
55. How would you implement optimistic UI updates for POST/DELETE using RTK Query or Thunk?
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Basics
Slice
Actions
Reducers
RTK Query
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Scenario Based
04 / 05

4. How do you persist Redux state across reloads while using RTK Query?

Difficulty: 7/10
state persistence, RTK Query cache, middleware

Persisting Redux State with RTK Query

RTK Query manages server cache automatically in memory, but this cache is lost when the page reloads. To persist specific parts of your Redux state across reloads, including RTK Query data if needed, you can integrate persistence middleware such as redux-persist. However, RTK Query cache persistence is typically avoided because it can lead to stale data unless refetched on app start.

Best Practices for State Persistence with RTK Query
  1. 1

    1. Persist Only Critical State: Use redux-persist for slices like authentication, user preferences, or local UI state.

  2. 2

    2. Avoid Persisting RTK Query Cache: Let RTK Query refetch data automatically when components mount to ensure freshness.

  3. 3

    3. Trigger Refetch on Rehydration: If persistence is necessary, use api.util.invalidateTags() or manual refetching after rehydration.

  4. 4

    4. Combine with createAsyncThunk (if needed): You can persist results from thunks while letting RTK Query handle real-time API synchronization.

Example: Persisting Redux State with RTK Query

In this setup, redux-persist stores the authentication state in localStorage while RTK Query refetches server data automatically. This ensures critical state is retained across reloads without risking outdated cached responses.

Scenario Questions

0-2 years experience

  1. 1How would you set up your Redux store so that an auth token fetched via RTK Query remains available after the user refreshes the page?
  2. 2If you add redux-persist to your store, what happens to the RTK Query cache when the app reloads, and how would you verify it works?

2-5 years experience

  1. 1You notice that after a page reload the UI shows stale data from an RTK Query endpoint even though the persisted state contains the latest token. Walk me through how you'd debug and fix it.
  2. 2Explain the trade‑offs between persisting the whole RTK Query cache versus persisting only specific slices of state in a medium‑sized feature.

5-8 years experience

  1. 1Design a strategy to persist RTK Query cache in a large application with multiple tabs, ensuring that cache invalidation works across tabs and after a reload.
  2. 2How would you handle versioning of persisted RTK Query state so that a change in the API schema doesn’t break existing users?
  3. 3What considerations would you make for performance and storage limits when persisting large query results?

8+ years experience

  1. 1Your organization wants to replace a home‑grown localStorage persistence with a unified Redux Toolkit persistence approach for all services that use RTK Query. What architectural concerns and rollout plan would you propose?
  2. 2Discuss the security implications of persisting sensitive data returned by RTK Query endpoints and how you would mitigate risks across multiple teams.

Follow-up Questions

  • What are the pros and cons of persisting the entire RTK Query cache versus only selected endpoints?
  • How would you test that the persisted state correctly restores after a hard refresh?
  • Can you compare using redux-persist with a custom localStorage solution for this use case?
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