Software Developer Interview Questions
10 curated questions with evaluation guidance for hiring managers.
Walk me through a project where you had to make significant architectural decisions. What trade-offs did you consider?
Look for structured thinking about scalability, maintainability, and cost. Strong candidates discuss specific trade-offs (e.g., monolith vs microservices) and explain why they chose one approach over another given the constraints.
How do you approach debugging a production issue that you cannot reproduce locally?
Expect a systematic methodology: checking logs, monitoring dashboards, reproducing with production-like data, using feature flags or canary deployments. Red flag if they jump to code changes without diagnosis.
Explain the difference between optimistic and pessimistic concurrency control. When would you use each?
Should explain locking strategies clearly. Optimistic for low-contention reads, pessimistic for high-contention writes. Bonus if they mention real-world examples like database transactions or distributed systems.
Describe your experience with code reviews. What do you look for when reviewing someone else's code?
Look for emphasis on readability, correctness, edge cases, and performance — not just style. Strong candidates mention mentoring junior developers and learning from reviews they receive.
How do you decide when to refactor existing code versus building a new solution?
Expect pragmatic reasoning: technical debt assessment, business impact, timeline constraints. Avoid candidates who always want to rewrite or who never refactor.
Tell me about a time you had to learn a new technology quickly for a project. How did you approach it?
Look for a structured learning approach: official docs, small proof-of-concept, community resources. Strong candidates mention how they evaluated whether the technology was the right fit.
How do you ensure your code is testable? Walk me through your testing strategy for a recent feature.
Should mention unit tests, integration tests, and possibly E2E tests. Look for understanding of test boundaries, mocking strategies, and coverage goals without over-testing.
What is your approach to handling technical debt in a fast-moving team?
Look for balance between shipping and quality. Strong answers include tracking debt, allocating sprint time for cleanup, and making incremental improvements rather than large rewrites.
Explain how you would design a rate limiter for an API. What algorithms would you consider?
Should mention token bucket, sliding window, or leaky bucket algorithms. Look for discussion of distributed rate limiting challenges, storage options (Redis, in-memory), and edge cases.
How do you handle disagreements with teammates about technical approaches?
Look for maturity: presenting data, prototyping alternatives, being open to compromise. Red flag if they insist on always being right or avoid conflict entirely.
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