React Interview Questions to Expect

React's surface area is huge, and question lists treat every corner as equally likely. They are not. This section covers the concepts that actually decide most rounds, so you can practice the real distribution. Four clusters dominate:

• Hooks mechanics: the rules of hooks, what goes in a useEffect dependency array, cleanup functions, and the stale closure bug where an effect or callback sees an old state value.
• Rendering: what triggers a re-render, how reconciliation diffs trees, and why stable keys matter in lists.
• State design: lifting state, controlled against uncontrolled inputs, and when context fits against an external store.
• Performance: React.memo, useMemo, useCallback, and when each is noise rather than help.

Interviewers probe the why behind each. Reciting that keys need to be unique scores nothing; explaining what React does with a key during a list reorder does.

Most React rounds include building a small component live. The recurring exercises are stable across companies:

• Fetch a list from an API, render it, and add a text filter.
• Add debouncing to a search input and cancel stale requests.
• Build a form with validation and controlled inputs.
• Write a counter or timer that cleans up its effect correctly.
• Extract a custom hook from repeated logic.

A front-end engineer interviewing for a mid-level product role, for example, might build the fetch-and-filter list, then get pushed on loading states, error states, and what happens when the component unmounts mid-request. The extensions are where rounds are won; the base exercise is table stakes.

Drilling these under a clock with follow-up questions is what makes them automatic; the mock interview page covers running timed sessions where the interviewer pushes back.

Senior screens shift from mechanics to judgment. Expect questions on state architecture: what lives in component state, what belongs in a store, how server state differs from UI state, and where caching sits. Rendering performance questions get concrete: finding the source of a slow interaction, deciding between memoization and restructuring, and reading a profiler flame graph.

Server-side rendering and hydration appear where the team runs a framework on top of React: what hydration is, why mismatches happen, and what moving work to the server buys. Testing questions focus on strategy, what you test at component level against end to end, more than on any library's API.

Interview formats and how a front-end loop typically assembles these rounds are covered in the interview types hub.

Watching tutorials builds recognition, not recall, and the round tests recall under observation. The fix is reps in the round's actual shape: build the standard exercises from an empty file, narrate while typing, and answer interruptions without losing the thread. Question sets for adjacent stacks, including plain JavaScript fundamentals that React rounds still open with, live in the question banks hub.

One honest note: React interviews nearly always run in a shared editor or with your screen visible, and anything on that screen is visible to the interviewer. An assistant belongs in preparation and practice there, not in the shared-screen round itself. For legitimate live use, SubcueAI's overlay stays local to your machine and no bot joins the call; setup for practice sessions is on the tutorial page.