AdvancedTechnical
5 min
Blue-Green vs Canary Deployments with Feature Flags
DeploymentsCI/CDRelease Engineering
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Interview Question
Compare blue-green and canary deployments. How would you integrate feature flags to reduce risk during production rollouts?
Key Points to Cover
- Blue-green: instant switch with two identical environments
- Canary: progressive exposure and metrics-based promotions
- Feature flags to decouple release from deploy and enable quick rollback
- Guardrails: automated metrics/SLO checks, kill switches, blast-radius limits
Evaluation Rubric
Explains differences and trade-offs35% weight
Uses feature flags to mitigate risk25% weight
Defines promotion/rollback criteria20% weight
Limits impact with staged rollouts20% weight
Hints
- 💡Automate rollback on SLO regressions.
Common Pitfalls to Avoid
- ⚠️Confusing deployment strategies with feature flagging (they are complementary, not interchangeable).
- ⚠️Insufficiently testing the inactive environment in blue-green deployments before traffic switch.
- ⚠️Not defining clear, measurable promotion criteria for canary deployments.
- ⚠️Over-reliance on manual monitoring during canary rollouts, leading to slow detection.
- ⚠️Failing to have a clear rollback plan for both blue-green and canary strategies, including how feature flags are managed during rollbacks.
Potential Follow-up Questions
- ❓Where do you enforce change freezes?
- ❓How do flags interact with caching?
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