Engineering / backend developer interview questions
Top backend developer interview questions
Top backend developer interview questions for APIs, databases, reliability, security, scalability, and service ownership.
Practice set
Top backend developer questions you are likely to hear
Each prompt includes a quick answer cue so you can practice the shape of the response, not just memorize a script.
Question
How would you design an API for a new feature?
Clarify consumers, resource model, validation, errors, versioning, auth, and observability.
Question
Tell me about a database design decision you made.
Explain access patterns, data relationships, constraints, indexing, and migration risk.
Question
How do you handle slow queries in production?
Discuss query plans, indexes, cardinality, caching, pagination, and measuring impact.
Question
How would you make a service more reliable?
Talk about timeouts, retries, idempotency, alerting, graceful degradation, and incident learning.
Question
How do you secure an API endpoint?
Cover authentication, authorization, input validation, rate limits, secrets, logging, and least privilege.
Question
Tell me about a time you migrated a system safely.
Mention compatibility, backfill, rollout, monitoring, rollback, and communication.
Question
How do you choose between synchronous and asynchronous processing?
Discuss user latency, reliability, retry semantics, ordering, and operational complexity.
Question
How would you investigate a spike in error rate?
Start with scope, recent deploys, dependencies, logs, traces, and customer impact.
Question
What makes an endpoint easy for other engineers to use?
Point to predictable contracts, docs, errors, examples, and stable behavior under edge cases.
Question
How do you balance scalability with simplicity?
Show when you defer complexity and what signals would justify a more scalable design.
Pressure moments to expect
- You need to be precise about reliability without overbuilding the answer.
- The interviewer asks for edge cases after your first design.
- You need to explain production tradeoffs clearly.
Where Kairo fits
Kairo helps keep requirements, risks, data flow, and operational safeguards in view during technical answers.
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