What determines when a cached DNS record expires?

• A. The TTL (time-to-live) value set for the record.
• B. The time since the last successful lookup.
• C. The current cache size.
• D. The zone's refresh interval.

Answer: (A)

Cached DNS records expire based on the TTL value attached to the record. The TTL (time-to-live) tells resolvers how long that record can be kept in cache. When a response is received, the resolver stores the answer and starts a countdown equal to the TTL; once that time passes, the entry is considered expired and the resolver must re-query to refresh it. The TTL is set by the domain’s authoritative zone, so expiration timing comes from that value, not from how recently a lookup succeeded, the current cache size, or the zone’s refresh interval. For example, a TTL of 3600 seconds means the cache entry stays valid for one hour before requiring a new lookup.