What happens to the DNS resolution result after a query?

• A. The result is cached by the resolver and returned to the client
• B. The result is not cached and must be recomputed
• C. The result is stored on the root servers
• D. The client must re-query each time

Answer: (A)

Caching is the key idea. After a DNS query completes, the resolver stores the answer in its cache and returns that result to the client. Those cached records stay usable for the time specified by their TTL, so future requests for the same name can be answered from the cache instead of going out to upstream servers again. Root servers don’t hold a cache of every individual domain’s answer; they help direct resolvers to the right authoritative servers. If the cached entry’s TTL expires, the resolver must refresh the information by querying again.