Which statement about TTL is true?

Which statement about TTL is true?

• A. TTL by itself is a complete eviction policy.
• B. TTL guarantees data freshness without any further mechanisms.
• C. TTL is an expiration setting on individual cache keys that is typically used with an eviction policy such as LRU.
• D. TTL prevents cache stampedes.

Answer: (C)

TTL is the expiration time assigned to individual cached keys. It marks how long a value can stay in the cache before it’s considered stale, and it’s typically used alongside a separate eviction policy (such as LRU) that decides which item to remove when space is needed. TTL by itself doesn’t define a full eviction strategy, since it doesn’t handle capacity decisions or the exact item to evict. It also doesn’t guarantee data freshness, because data can change after it’s cached and TTL only controls when items expire, not whether they’re updated. Additionally, TTL does not prevent cache stampedes; when many clients hit after expiry, a spike can occur unless extra mechanisms are used to coordinate refreshes. So the statement that TTL is an expiration setting on individual cache keys used with an eviction policy like LRU is the best description.

TTL is the expiration time assigned to individual cached keys. It marks how long a value can stay in the cache before it’s considered stale, and it’s typically used alongside a separate eviction policy (such as LRU) that decides which item to remove when space is needed. TTL by itself doesn’t define a full eviction strategy, since it doesn’t handle capacity decisions or the exact item to evict. It also doesn’t guarantee data freshness, because data can change after it’s cached and TTL only controls when items expire, not whether they’re updated. Additionally, TTL does not prevent cache stampedes; when many clients hit after expiry, a spike can occur unless extra mechanisms are used to coordinate refreshes. So the statement that TTL is an expiration setting on individual cache keys used with an eviction policy like LRU is the best description.