Behavioral round

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1. Tell me about a production outage or serious incident you helped resolve.

   STAR rubric: tick what your answer covered

   • Situation: What failed, who was affected and how it was detected.
   • Task: Your role in the response and the first priority.
   • Action: How you limited impact, found the cause and verified the fix.
   • Result: Downtime or error numbers, and the alert, test or runbook added.

   What interviewers listen for

   • Mitigated before hunting the root cause
   • Used dashboards, logs or traces to narrow it down
   • Kept others informed during the incident
   • Added a lasting guard afterwards

   Red flags to avoid

   • Blaming a person
   • No numbers at all
   • Hot-fixing production with no review or rollback plan

2. Describe a time you made a slow service or query faster.

   STAR rubric: tick what your answer covered

   • Situation: What was slow and how it hurt users or costs.
   • Task: The target you set.
   • Action: How you profiled or used EXPLAIN, what you changed and why.
   • Result: Before and after latency or cost, and how you kept it from regressing.

   What interviewers listen for

   • Measured before changing anything
   • Found the real bottleneck
   • Checked the change with numbers
   • Thought about side effects

   Red flags to avoid

   • Guessing without measurement
   • Caching as a reflex with no invalidation plan
   • Claiming a speed-up with no figures

3. Tell me about a risky data or schema migration you planned or ran.

   STAR rubric: tick what your answer covered

   • Situation: The system, the data size and what had to change.
   • Task: What 'done safely' meant.
   • Action: The steps, safeguards and checks you used.
   • Result: Outcome, any surprises and what you'd repeat.

   What interviewers listen for

   • Planned for old and new code running together
   • Backfilled in safe batches
   • Had a rollback or roll-forward plan
   • Communicated the window and risk

   Red flags to avoid

   • One big-bang change on a live table
   • No backup or restore test
   • Ignoring lock or replication impact

4. Describe a time an API change broke a client, or nearly did.

   STAR rubric: tick what your answer covered

   • Situation: The API, the change and who used it.
   • Task: What you needed to fix or prevent.
   • Action: How you restored service and what guard you added (contract tests, versioning, deprecation).
   • Result: Impact and how later changes went.

   What interviewers listen for

   • Understood who depended on the API
   • Owned the fix and the communication
   • Changed the process, not just the code

   Red flags to avoid

   • 'The client should have handled it'
   • No follow-up guard
   • Hiding the incident

5. Tell me about a time you disagreed with a technical design, such as microservices, a database choice or a queue.

   STAR rubric: tick what your answer covered

   • Situation: The decision and why it mattered.
   • Task: What you wanted to change.
   • Action: How you argued your case and listened.
   • Result: What was decided and what you learned, even if you lost.

   What interviewers listen for

   • Understood the other view first
   • Brought evidence: a prototype, numbers, a failure mode
   • Committed once decided

   Red flags to avoid

   • Describing colleagues as foolish
   • Going around the team
   • Never accepting the outcome

6. Describe a security issue you found or fixed in a backend.

   STAR rubric: tick what your answer covered

   • Situation: What the issue was and how it was found.
   • Task: What needed protecting and how urgently.
   • Action: The fix, any data checks and who you told.
   • Result: Exposure found (if any), and the check, test or review step added.

   What interviewers listen for

   • Understood the real risk and who was exposed
   • Fixed the class of bug, not one instance
   • Handled disclosure responsibly

   Red flags to avoid

   • Downplaying the risk
   • Fixing quietly with no follow-up
   • Sharing sensitive details carelessly

7. Tell me about something you did to make on-call or operations less painful.

   STAR rubric: tick what your answer covered

   • Situation: What on-call looked like before.
   • Task: The goal you set.
   • Action: What you changed: alerts, SLOs, automation or docs.
   • Result: Pages per week or time saved, before and after.

   What interviewers listen for

   • Used data on pages or toil
   • Removed noise, not just silenced it
   • Improved runbooks, alerts or automation

   Red flags to avoid

   • Muting alerts without fixing causes
   • No measure of improvement
   • Doing it alone with no handover

8. Describe a backend feature where the requirements were unclear at the start.

   STAR rubric: tick what your answer covered

   • Situation: The feature and what was unclear.
   • Task: What you had to deliver and by when.
   • Action: How you clarified scope, designed for change and checked in.
   • Result: What shipped, how it was used, and what changed after feedback.

   What interviewers listen for

   • Asked questions to find the real need
   • Made assumptions explicit
   • Shipped in small steps and adjusted

   Red flags to avoid

   • Building everything up front
   • Never checking with users or product
   • Blaming the requirements