Backend Engineer Interview Questions
Questions for evaluating backend developers on APIs, databases, scalability, and system design.
Technical Questions
How would you design an API rate limiter that works across multiple server instances?
Follow-up questions
- What storage backend would you use?
- How would you handle burst traffic?
What to look for
Understanding of distributed systems, Redis/token bucket algorithms, and trade-offs between accuracy and performance.
How do you decide between SQL and NoSQL for a new feature?
Follow-up questions
- Give an example where you'd use each.
- How do you handle migrations?
What to look for
Data modeling intuition, understanding of consistency vs. availability trade-offs, and practical experience.
How do you ensure the security of user data in APIs you build?
Follow-up questions
- How do you handle authentication vs. authorization?
- What about input validation?
What to look for
OWASP awareness, defense-in-depth thinking, and practical security patterns.
Behavioral Questions
Tell me about a production incident you helped resolve. What was the root cause and what did you learn?
Follow-up questions
- How did you prevent it from happening again?
- What monitoring did you add?
What to look for
Incident response skills, blameless post-mortem thinking, and learning orientation.
Describe a technical decision you made that you later regretted. What would you do differently?
Follow-up questions
- How did you communicate the change?
- What did the team learn?
What to look for
Intellectual humility, willingness to revisit decisions, and growth mindset.
Situational Questions
A critical API endpoint is returning 500 errors for 5% of requests. How do you investigate?
Follow-up questions
- What logs would you check first?
- How do you reproduce intermittent failures?
What to look for
Systematic debugging approach, observability tooling knowledge, and prioritization.
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