Interview › Databases & Caching
What is the blast radius of a cache outage, and how do you make the app degrade gracefully?
Databases & Caching · Advanced level
Answer
A cache outage can cause anything from minor latency to full outage. I reduce blast radius with low timeouts, circuit breakers, DB fallback limits, stale-if-safe responses, local last-known-good data, and graceful feature degradation.
Technical explanation
Cache failure should not automatically become total service failure unless the cache is an intentional primary store.
Use low timeouts and circuit breakers to avoid tying up app threads.
Degrade non-critical features and protect DB fallback with rate limits.
Hands-on example
Failure policy:
Redis connect_timeout=50ms, read_timeout=50ms, max_retries=1.
Product miss: DB fallback with limiter.
Recommendations failure: omit module.
Feature config failure: use last-known-good local copy.
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