Interview questions / Backend Developer
Backend Developer interview questions
These are questions Backend Developer candidates often hear, with a short note on what a strong answer covers. Reading them helps; saying your answers out loud helps more.
Design a REST API for a simple to-do app. What endpoints and status codes would you use?
Name resources, verbs, status codes, and how you'd handle auth and errors.
How would you find and fix a slow database query?
Talk about query plans, indexes, N+1 queries, and checking the fix with real numbers.
SQL or NoSQL for a new project: how do you choose?
Tie the choice to data shape, consistency needs and query patterns, not preference.
How do you keep an API secure?
Cover authentication, authorisation checks on every request, input validation, rate limits and secrets handling.
Tell me about a production incident you helped resolve.
Explain detection, your actions, the root cause, and what you changed so it wouldn't recur.
How would you design a job that processes 1 million records a night?
Discuss batching, retries, idempotency, monitoring and what happens if it fails halfway.