Redux is a JavaScript library that helps manage state in React apps. If you are getting ready for a Redux developer interview, these 2026 Redux Interview Questions and Answers will help you learn the main ideas and feel more confident.
Here are 20 key Redux Interview Questions and Answers that often come up in interviews. The questions are split into two sections:
Redux Interview Questions (Basic)
The first section covers basic Interview Questions and Answers.
Q1. Benefits of Redux?
Answer:
- Maintainability: Redux is easier to maintain because it uses a clear code structure and organization.
- Organization: Redux enforces strict code organization, which makes the code more stable and easier to work with.
- Server rendering: Redux helps with server-side rendering, which improves the first load for users and helps with search engine optimization. The store created on the server is sent to the client.
- Developer tools: Redux offers tools that let developers see changes in real time, making it easier to track what happens in the app.
- Ease of testing: The first rule of writing testable code is to write small functions that do only one thing and that are independent. Redux’s code is made of functions that used to be: small, pure, and isolated.
Q2. How Distinct from MVC and Flux?
Answer:
As far as the MVC structure is concerned, the data, presentation, and logic layers are well-separated and handled. Changing to an application, even in a smaller position, may require many changes to the application. This happens because data flow exists bidirectionally as far as MVC is concerned. Maintenance of MVC structures is hardly complex, and Debugging also requires a lot of experience.
Flux is similar to Redux. It uses a pattern that tracks changes to the app state, event subscriptions, and the current state, all connected through components. In Redux, callback payloads are sent out to update the state.
Q3. Functional programming concepts?
Answer:
Redux uses several functional programming concepts, including:
- Functions are treated as First-class objects.
- Capable of passing functions in the format of arguments.
- Capable of controlling flow using recursions, functions, and arrays.
- Helper functions like reduce, map, and filter are used.
- Functions can be linked together.
- The state is not changed directly.
- You do not need to prioritize the order of code execution.
Q4. Redux change of state?
Answer:
For a release of action, a change in state is applied to the application; this ensures that the intent to change the state is achieved.
Example:
- The user clicks a button in the application.
- A function is called in the form of a component.
- So now an action gets dispatched by the relative container.
- This happens because the prop (which was just called in the container) is tied to an action dispatcher using mapDispatchToProps (in the container).
- Reducer captures the action, internally executes a function, and returns a new state with specific changes.
- The state change is known to the container and modifies a specific prop in the component via the mapStateToProps function.
Q5. Where can Redux be used?
Answer:
Redux is mainly used in combination with React. It also has the ability to get used to other view libraries too. Some of the famous entities include AngularJS, Vue.js, and Meteor. It can be combined with Redux easily. This is a key reason for Redux’s popularity within its ecosystem. So many articles, tutorials, middleware, tools, and boilerplates are available.
Redux Interview Questions (Advanced)
Now, let’s look at some advanced Interview Questions.
Q6. What is the typical data flow in a React + Redux app?
Answer:
A callback from the UI component dispatches an action with a payload; these dispatched actions are intercepted and handled by the reducers. This interception will generate a new application state. From here, actions will propagate down a component hierarchy from the Redux store. The diagram below depicts the entity structure of a Redux+React setup.
Q7. What is stored in Redux?
Answer:
The Store holds the application state and provides helper methods for accessing it. Register listeners and dispatch actions. There is only one Store while using Redux. The Store is configured via the createStore function. The single Store represents the entire state. R
ducers return a state via action.
export function configureStore(initialState) {
return createStore(rootReducer, initialState);
}The root reducer is a collection of all reducers in the application.
const rootReducer = combineReducers({
donors: donorReducer,
});Let us move to the next Redux Interview Questions.
Q8. Explain Reducers in Redux?
Answer:
The state of a store is updated using reducer functions. A stable collection of reducers forms a store, and each Store maintains a separate state. To update the donor array, we should define a donor application.
The reducer is as follows.
export default function donorReducer(state = [], action) {
switch (action.type) {
case actionTypes.addDonor:
return [...state, action.donor];
default:
return state;
}
}The reducers receive the initial state and action. Based on the action type, it returns a new state for the Store. The state maintained by reducers is immutable. The given reducer holds the current state and action as arguments and then returns the next state.
state:function handelingAuthentication(st, actn)
{
return _.assign({}, st,
{
auth: actn.pyload
});
}Q9. Redux workflow features?
Answer:
- Reset: Allow to reset the state of the Store
- Revert: Rollback to the last committed state
- Sweep: All disabled actions that you might have fired by mistake will be removed
- Commit: Makes the current state the initial state
Q10. Explain actions in Redux?
Answer:
Actions in Redux are functions that return an action object. The action type and action data are packed into the action object. This also allows a donor to be added to the system. Actions send data between the Store and the application. The actions produce all information retrieved by the Store.
export function addDonorAction(donor) {
return {
type: actionTypes.addDonor,
donor,
};
}Internal actions are JavaScript objects that include a type property.
Q11. What is Redux Toolkit (RTK)?
Answer:
Redux Toolkit (RTK) is the official library for building Redux apps. It makes state management easier by reducing boilerplate and offering tools like configureStore for setting up the store, createSlice for reducers and actions, and createAsyncThunk for async tasks. RTK helps you write cleaner, easier-to-maintain Redux code that follows best practices.
Q12. What is createSlice in Redux Toolkit?
Answer:
createSlice is a tool in Redux Toolkit that combines the initial state, reducers, and action creators in one file. It automatically creates action types and action creators from your reducer functions. This reduces boilerplate, improves readability, and keeps related logic organized.
Q13. What is the difference between Redux and Redux Toolkit?
Answer:
| Redux | Redux Toolkit |
| Requires more boilerplate code | Minimal boilerplate |
| Manual store configuration | Automatic configuration |
| Actions and reducers are created separately | Uses createSlice |
| Middleware added manually | Includes default middleware |
Q14. What is createAsyncThunk?
Answer:
createAsyncThunk helps manage async tasks like API calls. It automatically creates pending, fulfilled, and rejected action types, making async state management easier.
Q15. What are Redux Hooks?
Answer:
Redux Hooks are functions from React Redux that let functional components work with the Redux store without connect(). The main hooks are useSelector, which reads data from the Store, and useDispatch, which sends actions. Hooks make Redux easier to use and reduce boilerplate.
Redux provides hooks for functional components:
- useSelector() – Reads data from the Redux store.
- useDispatch() – Dispatches actions to update the Store.
These hooks usually replace the need for connect() in React apps.
Q16. What is Middleware in Redux?
Answer:
Middleware sits between dispatching an action and reaching the reducer. It is commonly used for logging, handling asynchronous operations, reporting errors, and making API requests. Middleware helps keep reducers pure while managing side effects separately.
Examples:
- Redux Thunk
- Redux Saga
- Redux Logger
Q17. What is Immutable State in Redux?
Answer:
Immutable state in Redux means you never change the original state directly. Instead, you make a new copy with the updates. This makes your app easier to understand, keeps updates predictable, and helps React update the UI efficiently.
Q18. What is the purpose of configureStore()?
Answer:
configureStore() is a function provided by Redux Toolkit that simplifies the creation of a Redux store. It automatically combines reducers, enables the Redux DevTools Extension for easier debugging, and includes useful default middleware such as thunk. This reduces the amount of boilerplate configuration required, promotes best practices, and makes Redux applications easier to set up, maintain, and scale.
Q19. What are Redux DevTools?
Answer:
Redux DevTools are powerful browser extensions that help developers debug and monitor Redux applications in real time. They display every dispatched action, show how the application state changes after each action, and allow time-travel debugging by replaying or reversing actions. This makes it easier to identify bugs, understand data flow, optimize state management, and improve the overall development experience.
Q20. What are the best practices for using Redux in 2026?
Answer:
- Use Redux Toolkit for all new projects.
- Keep the Redux state minimal.
- Store only global application state.
- Keep reducers pure and immutable.
- Use createAsyncThunk for API calls.
- Normalize complex state when necessary.
- Use selectors to access store data efficiently.
- Avoid unnecessary state updates to improve performance.
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