IntermediateScenario
10 min
Cache Stampede / Thundering Herd
CachingPerformanceReliability
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Interview Question
A cache eviction triggers a surge of requests to the origin, causing overload. How do you diagnose and prevent cache stampede?
Key Points to Cover
- Identify synchronized TTL expirations causing origin spikes
- Implement jittered TTLs and request coalescing/locking
- Use stale-while-revalidate and early refresh
- Protect origin with rate limits and circuit breakers
- Instrument cache hit ratio and origin QPS
Evaluation Rubric
Recognizes synchronized expirations30% weight
Applies anti-stampede patterns30% weight
Shields origin effectively20% weight
Tracks CHR and origin load20% weight
Hints
- 💡Look for aligned TTLs across nodes.
Potential Follow-up Questions
- ❓How to do request collapsing in your stack?
- ❓What about per-key rate limits?
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