IntermediateScenario
10 min
CDN Invalidation Storm Causes Origin Overload
CDNCachingPerformance
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Interview Question
A misconfigured deployment invalidates most CDN cache objects at once, flooding the origin. What’s your triage and prevention plan?
Key Points to Cover
- Throttle/queue invalidations and pause non-critical purges
- Enable stale-while-revalidate and serve-stale-on-error
- Raise origin capacity or enable origin shield/tiers temporarily
- Fix cache keys/headers to limit unnecessary purges
- Add guardrails and change reviews for invalidation jobs
Evaluation Rubric
Stabilizes CDN and origin quickly30% weight
Uses correct caching semantics30% weight
Manages origin capacity/shielding20% weight
Prevents future storms via guardrails20% weight
Hints
- 💡Invalidations should be scoped by path/prefix.
Potential Follow-up Questions
- ❓What KPIs show healthy cache behavior?
- ❓How to test invalidations safely?
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