SeniorCI/CD & DevOps for QA
How do you implement blue-green deployments?
- blue-green
- zero-downtime
- deployment strategy
Answer it first, then compare. Nothing here is saved or scored.
Model answer
Blue-green: maintain two identical production environments (blue and green). Process: (1) Blue is live, deploy new version to green. (2) Run smoke tests against green. (3) Switch load balancer to green. (4) Monitor for issues. (5) If problems, instantly switch back to blue. Benefits: zero-downtime deployment, instant rollback. Challenges: database state must be compatible with both versions (expand-contract migrations), session management during switch, cost of running two environments. Suitable for: critical applications where rollback speed matters.
What interviewers listen for
- Pipeline shapeYou design stages by failure cost and runtime budget, not by tool feature lists.
- Parallelisation craftYou can shard a real suite and explain the state-isolation choices you made.
- Quality gatesYou know which checks block merge, which warn, and why those defaults are correct.
- Shift-left fluencyYou talk about ownership transfer, not just earlier execution.