Software Engineer Interview
Questions & Answers

Strong answers cover the full system design: API layer, hash generation algorithm (base62 encoding), database schema (original URL + short code + click count), caching layer (Redis for hot URLs), handling redirects (301 vs 302), analytics considerations, and scalability at 100M URLs. Candidates who ask clarifying questions (read vs write heavy? analytics required?) before designing demonstrate senior-level thinking.

Structured debugging approach: (1) gather information — logs, error rates, timeline of when it started; (2) form hypotheses based on recent deployments or changes; (3) isolate the blast radius; (4) test hypotheses from most to least likely; (5) fix and verify, then document the root cause. Candidates who start with "I'd add more logging" without a systematic approach signal junior-level thinking.

REST: resource-based, multiple endpoints, predictable caching, good for public APIs and simple CRUD operations. GraphQL: query-based, single endpoint, client specifies exact data needed, eliminates over-fetching and under-fetching, better for complex data relationships and rapidly evolving front-end requirements. Neither is universally superior — the answer depends on the use case and team familiarity.

Code review process (what you review for, how you give feedback), automated testing (unit, integration, E2E), CI/CD pipeline gates, coding standards/linting, documentation practices, and design reviews for larger changes. Strong answers include specific examples from your experience and acknowledgment that code quality is a team culture outcome, not just a process one.

Systematic approach: (1) use EXPLAIN/EXPLAIN ANALYZE to understand the query plan; (2) identify missing indexes on filtered and joined columns; (3) check for N+1 query patterns; (4) evaluate whether data can be denormalised for read performance; (5) consider query result caching; (6) evaluate whether the query can be paginated or batched. Show you profile first and optimise second.

Structure your answer as a 60-second professional narrative: where you have been (your background), what you have done (your strongest achievement), and where you are going (why this role). Lead with your most relevant experience, not your entire career history. End with why you are excited about this specific opportunity.

Choose a genuine weakness that you have actively worked to improve. The structure is: name the weakness → show self-awareness of its impact → describe the concrete step you took to address it → show the improvement. Never say "I work too hard" — interviewers recognise this as evasion and it damages your credibility.

Use the STAR method (Situation, Task, Action, Result) but add a fifth element: what you learned. Choose a real failure, not a disguised success. Show you can take responsibility without making excuses, and demonstrate that the lesson changed your behaviour in a specific, verifiable way.

Be honest but constructive. Acceptable reasons: seeking greater scope, new challenge, skills you can not develop in the current role, or company-level changes (restructuring, direction shift). Never speak negatively about your current employer or manager — it signals you will do the same to the prospective employer in future conversations.

Describe the conflict specifically, show that you sought to understand the other person's perspective, and explain the resolution approach you took. Interviewers are assessing your emotional intelligence and whether you escalate or resolve. Avoid stories where you were right and they were wrong — choose a story where both parties grew.

Describe your specific prioritisation system: impact × urgency matrix, stakeholder alignment, or a specific tool or process you use. Then give an example where you applied it under real pressure. Show that your system is systematic rather than reactive, and that you communicate proactively when priorities change.

Choose an achievement that is specific, measurable, and relevant to the role. Lead with the result ("I reduced our error rate by 40% in 90 days"), then explain the context, challenge, and what you specifically did that drove the result. Show your ownership and impact, not just your team's work.

Be honest about your ambitions while showing that this role is a genuine step in that direction — not a stopgap. Hiring managers want to invest in people who will grow with the organisation. Show that your 5-year goal requires the specific skills and experience this role provides, making your ambition an asset for both sides.

Research before the interview and make the answer specific: cite their product, a recent company development, something about their culture or team, or a professional aspect of this particular role that matches your goals. Generic answers ("I love your values") signal you did not do the research. Specific answers signal genuine interest.

Always have 3–5 questions prepared. Ask about the biggest challenge in this role, what success looks like in the first 90 days, how the team operates, and the interviewer's own experience at the company. Never ask about salary, benefits, or holidays in a first interview. Questions show interest, strategic thinking, and that you care enough to have done research.