A cached response must be invalidated when its underlying record changes. Which approach is most reliable?

1. A Rely on TTL expiry alone
2. ✓ B Explicitly DEL the cache key in the same code path that writes the record (correct answer)
3. C Use Pub/Sub without subscribers
4. D Reduce maxmemory

Shortcut: Write-through invalidation removes the stale entry deterministically at the moment of change. TTL alone leaves a stale window equal to the remaining TTL.