Top 15 Backend Engineer Interview Questions

Describe a production incident you handled. Walk me through your response.

💡 Tip: Show calm under pressure, systematic diagnosis, and post-mortem learnings.

Tell me about a system migration you led or contributed to.

💡 Tip: Show planning, risk mitigation, and rollback strategies.

Describe a time you implemented monitoring or alerting that caught a real issue.

💡 Tip: Show proactive thinking and how the monitoring paid off.

Describe a time you had to scale a system to handle increased load.

💡 Tip: Show capacity planning and horizontal/vertical scaling decisions.

Tell me about a data pipeline you built or improved.

💡 Tip: Focus on reliability, monitoring, and handling edge cases.

Describe a time you had to debug a distributed system issue.

💡 Tip: Show tracing, correlation IDs, and systematic investigation.

How do you approach security in backend systems?

💡 Tip: Cover authentication, authorization, input validation, and data protection.

How do you handle backward compatibility when changing APIs?

💡 Tip: Discuss versioning, deprecation policies, and communication with consumers.

How do you approach writing tests for backend services?

💡 Tip: Cover unit, integration, contract testing, and mocking strategies.

How do you document your APIs and systems?

💡 Tip: Show commitment to documentation and developer experience.

Tell me about a time you designed and built a scalable API.

💡 Tip: Discuss design decisions — REST vs GraphQL, pagination, rate limiting, versioning.

Tell me about a time you chose between different database technologies.

💡 Tip: Show evaluation criteria — query patterns, scale needs, consistency requirements.

Describe a time you optimized a slow database query.

💡 Tip: Be specific — query plans, indexing, denormalization, caching strategies.

Tell me about implementing distributed systems or microservices.

💡 Tip: Discuss tradeoffs — complexity, consistency, deployment independence.

Tell me about implementing caching in a production system.

💡 Tip: Discuss cache invalidation, TTL strategies, and consistency tradeoffs.