hard20 pts · first answer countscachingperformancesystem-design

Cache stampede on a hot key

The cached home-page feed key expires every 5 minutes. At expiry, thousands of concurrent requests miss the cache at once and overload the database. Which approach best prevents this?

A.Remove the TTL so the key never expires and never changesB.Increase the database connection pool to 5,000C.Let only one request rebuild the value (lock or single-flight) while others serve the stale value, and add random jitter to TTLsD.Lower the TTL to 5 seconds so the cache is always fresh

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