SeniorCI/CD & DevOps for QA
How do you implement feature flags and test them?
- feature flags
- gradual rollout
- testing strategy
Answer it first, then compare. Nothing here is saved or scored.
Model answer
Implementation: (1) Feature flag service (LaunchDarkly, Unleash, or custom). (2) Wrap new features in flag checks. (3) Default flags to off, enable gradually (percentage rollout, user targeting). Testing: (4) Test both flag states (on and off) in CI. (5) Test flag combinations if flags interact. (6) Test flag evaluation performance (should be fast, cached locally). (7) Clean up old flags regularly, they accumulate and become tech debt. (8) Use flags for operational safety (kill switches for expensive features) and gradual rollouts.
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.