Full Stack developer interview questions

A controlled input takes its value from React state and updates through onChange.

React.memo skips re-rendering a component when its props are shallowly equal.

Trigger the request in useEffect or a data library such as React Query, handle loading and error states, and cancel or ignore stale responses.

Lift state when two nearby components share data.

A custom hook is a function starting with use that calls other hooks.

An access token is short-lived and sent on each API call.

SameSite=Lax or Strict stops the browser from sending cookies on most cross-site requests, which blocks classic CSRF.

A salt is random data mixed into the hash so two users with the same password get different hashes.

A middleware reads the cookie or Authorization header, verifies the JWT or session, and attaches req.user.

OAuth lets the user sign in with a provider such as Google without sharing their password with you.

The user requests a reset

A Dockerfile packages Node, dependencies, and start command so the app runs the same on every machine.

Platforms such as Render, Railway, or AWS inject env vars into the process at runtime.

A reverse proxy such as nginx receives public traffic and forwards it to Express.

A process manager can start a new worker, wait until it listens, then stop the old one.

Atlas rejects connections from IPs that are not on the allowlist.

Query the UI the way a user would, by role, label, and text, not by component internals.

Replace the network layer with a stub that returns canned JSON so tests stay fast and offline.

Supertest issues HTTP requests against your Express app without opening a real port.

A stub returns prepared data so the unit under test can run.