Which statement best describes TTL (Time To Live) in caching?

Which statement best describes TTL (Time To Live) in caching?

• A. A strategy to always keep data in cache forever.
• B. An optional technique to compress cache entries.
• C. A global TTL that applies to all items.
• D. An expiration setting on individual cache keys that automatically removes them after a set duration.

Answer: (D)

TTL in caching is an expiration setting tied to each cache entry. It defines how long that specific item remains valid in the cache. Once the set duration passes, the item is considered expired and is typically removed or refreshed on the next access. This per-item control helps keep data fresh and prevents the cache from growing with stale data. It's not about keeping data forever, not about compressing entries, and it's not inherently a single global setting for all items—the core idea is per-key expiration. For example, caching a user profile for five minutes means that after five minutes, the next request will fetch updated data and re-cache it.

TTL in caching is an expiration setting tied to each cache entry. It defines how long that specific item remains valid in the cache. Once the set duration passes, the item is considered expired and is typically removed or refreshed on the next access. This per-item control helps keep data fresh and prevents the cache from growing with stale data. It's not about keeping data forever, not about compressing entries, and it's not inherently a single global setting for all items—the core idea is per-key expiration. For example, caching a user profile for five minutes means that after five minutes, the next request will fetch updated data and re-cache it.