Redux Interview Questions and Answers

What are the core Redux concepts?

A single store holds state; actions describe what happened; pure reducers take (state, action) and return the next state immutably; components dispatch actions and select state.

Why must reducers be pure and immutable?

Redux compares references to detect changes and enable time-travel debugging. A reducer must return a new state object, never mutate the existing one.

What is Redux Toolkit?

The official, recommended way to write Redux — it reduces boilerplate, uses Immer so you can 'mutate' drafts safely, and includes createSlice, the store setup and RTK Query.

When do you actually need Redux?

For complex, high-churn global client state shared across many parts of the app. For server data, React Query/SWR are usually better; for simpler global state, Context or Zustand.

Redux vs Context — what's the difference?

Context is a transport mechanism; Redux is a full state container with a single store, selectors, middleware and devtools. Context alone re-renders all consumers; Redux enables fine-grained subscriptions.