A cache-aside implementation suffers a thundering herd when a hot key expires. Which mitigation is most appropriate?

1. A Remove the TTL entirely
2. ✓ B Use a short-lived lock so one caller repopulates while others serve stale or wait (correct answer)
3. C Increase the cache size
4. D Switch to allkeys-random

Shortcut: A mutex or lock key ensures a single rebuild on expiry. Adding TTL jitter and probabilistic early refresh further spreads the load.