React mock interviews
Almost every frontend resume says React, so a React round is less about whether you have used it and more about whether you know why it re-renders, what a hook captures, and where state should live. That is the part tutorials skip.
Rounds with Sia from ₹99 · Live interviews with a working engineer from ₹299 · Pay per session
What a React round covers
Rendering and reconciliation
What triggers a render, what React compares, and why keys matter in a list. Expect to explain a re-render you did not expect.
Hooks, properly
useState batching, useEffect dependencies and cleanup, stale closures, and when useMemo and useCallback help — and when they only add noise.
State and data flow
Local state, lifted state, context and a store: which you would use for what, and what each costs in re-renders.
Performance and structure
Finding a slow component before memoising it, splitting code, and how you would structure a feature so it stays easy to change.
React interview questions you might be asked
Not a list to memorise. Each is the kind of opening a real round uses, with what a strong answer covers — the follow-ups depend on what you say.
A useEffect fetches data and runs in an infinite loop. Why?
Something in its dependencies changes on every render — often an object or function created inline. A strong answer finds the dependency and gives the fix that keeps it stable.
A list re-renders badly when you add an item to the top. What is the likely cause?
Index used as the key, so React matches the wrong items. Stable ids as keys fix it, and the answer explains how React uses keys to match elements.
You clicked "+1" three times quickly and the counter went up by one. Why?
Each update read the same stale value. The updater form, setCount(c => c + 1), works from the latest state.
A whole page re-renders when you type in one input. How do you find out why, and what do you change?
Profile first, then move the state down to where it is used, or split the context. Memoisation comes after, not before.
When would you not put state in context?
When it changes often and many components read it: every consumer re-renders on every change. Context suits values that rarely change, like the theme or the signed-in user.
Answer questions like these in a scored round and see exactly where your answer fell short.
What the interviewer is listening for
The signal is whether you can explain React in terms of what happens on each render, not in terms of which hook to use. Candidates who reason from the render outwards score above those who know the API by heart.
Where candidates lose marks
- Wrapping everything in useMemo and useCallback "for performance".
- Listing hooks without being able to explain a missing dependency bug.
- Putting all state in context or a global store by default.
Two ways to interview
A round with Sia, on your own
One question at a time with real follow-ups on what you actually said. Choose three, five or eight questions. Scored the moment you finish, with a written breakdown across technical depth, problem solving and communication.
A live interview with an engineer
Forty minutes over Zoom with someone who runs React interviews for a living. They score five criteria and write up what to fix, and you keep a numbered certificate for the session.
Choose React as your stack in the frontend or full-stack track.
Questions about React interviews
Which track should I pick for a React round?
React can be chosen as your stack in the frontend and full-stack tracks. Frontend for a round on the browser and the UI, full-stack if the job covers the API behind it too.
Is a React round right for a fresher?
Yes. Most fresher frontend interviews are React interviews. Beginner difficulty keeps to props, state, effects and lists before performance and architecture.
Do I need to know Next.js or Redux?
Only if they are on your resume or in the job description. The round is built around core React; a framework on your resume will be asked about.
How is a React round scored?
On the same five criteria as every round — technical depth, problem solving, communication, behavioural and code quality — with a written breakdown.
Read before your round
Other technologies
Interviews by track
Not sure which to book? The FAQ covers how sessions are scored, and candidate stories show what people did with the feedback.