Interview Questions for a Backend Developer
To interview a backend developer, focus on API design, database modeling and indexing, concurrency, caching, and reliability under load. This set probes how candidates design data models, handle transactions and failures, secure endpoints, and reason about scaling a service without compromising correctness or consistency.
Last updated
Run a backend interview around designing and reasoning about a service: data model, API, failure modes, and scale. Favor a design discussion plus a focused coding task over algorithm trivia, since correctness under concurrency and load is the real job.
Technical & Role-Specific
What to look for: Indexes speed reads but slow writes and add storage; chooses based on query patterns and selectivity, and verifies with the query planner.
What to look for: Optimistic for low-contention with version checks; pessimistic for high-contention critical sections; understands deadlock risk.
What to look for: Can name dirty reads, non-repeatable reads, and phantom reads, and maps them to read-committed vs serializable trade-offs.
What to look for: Token bucket or sliding window, where state lives (e.g. shared cache), per-key limits, and graceful 429 responses with retry headers.
What to look for: Identifies cacheable layers, picks TTL or invalidation strategy, and understands cache stampede and the thundering-herd problem.
What to look for: Transactions where possible, sagas or outbox pattern across services, idempotency, and compensating actions; avoids distributed two-phase commit naivety.
What to look for: EXPLAIN the plan, check for missing indexes or full scans, look at row counts and statistics, and consider pagination or partitioning.
What to look for: Knows offset pagination degrades; prefers keyset or cursor pagination, with stable ordering and consistent results under writes.
Behavioral
What to look for: Calm triage, clear communication, a real root-cause analysis, and durable fixes like alerts or runbooks, not just a hotfix.
What to look for: Won't cut corners on correctness, but can scope pragmatically and make the trade-off explicit to stakeholders.
What to look for: Awareness of over-engineering, building for plausible growth, and willingness to defer complexity until justified.
What to look for: Plans backward-compatible, online migrations in stages, backfills safely, and has a rollback plan rather than locking the table.
Situational / Problem-Solving
What to look for: Short-term: scale, add a queue, shed load, cache; longer-term: find the bottleneck with metrics and fix the architecture.
What to look for: Idempotency keys, unique constraints, dedup logic, and a safe backfill to remove existing duplicates.
What to look for: Timeouts, retries with backoff, circuit breakers, fallbacks, and not letting one dependency cascade into total failure.
What to look for: Considers write batching, async queues, sharding, read replicas for read offload, and the consistency trade-offs of each.
Backend Developer interview scorecard
Score every candidate on the same criteria, immediately after the interview, using evidence you actually heard rather than an overall impression. Agree the criteria with the panel before the first interview — deciding what counts after you have met people is how the loudest interviewer wins the debrief.
| Criterion | Evidence to record | Score 1-5 |
|---|---|---|
| Technical & Role-Specific | What the candidate actually said or did, in their own example — not your impression of it | 1 2 3 4 5 |
| Behavioral | What the candidate actually said or did, in their own example — not your impression of it | 1 2 3 4 5 |
| Situational / Problem-Solving | What the candidate actually said or did, in their own example — not your impression of it | 1 2 3 4 5 |
| Overall recommendation | Strong no / no / mixed / yes / strong yes, with the single reason that decided it | - |
Want this as a reusable document? Use the interview scorecard template.
Questions to avoid asking a Backend Developer
Exactly which questions are unlawful depends on where you are hiring, and the rules change — so treat this as the list of topics to route through your own employment counsel, not as a legal standard. The practical test that holds everywhere: if the answer could not change how the person does this job, you have no reason to ask it.
Related roles to hire
Frequently asked questions
How many interview rounds for a Backend Developer?
How important is system design for backend interviews?
Should I test SQL and database knowledge directly?
What distinguishes a senior backend developer in interviews?
Run these interviews structured, and compare candidates fairly
Pitch N Hire is an applicant tracking system with built-in interview scorecards. Load these questions into a scorecard so every interviewer assesses the same criteria and you can compare candidates side by side.
Free for 1 user · No credit card · Talk to a real hiring expert
See how much faster your team could hire
Get a personalized walkthrough of Pitch N Hire on your own roles and workflow. No slides, no obligation.
Prefer to talk? Book a demo Talk to sales View pricing
Free 1-user plan · No credit card · Talk to a real hiring expert
