Amazon Route 53 is both an Authoritative DNS service and Recursive DNS service. Authoritative DNS contains the final answer to a DNS query, generally an IP address. Clients (such as mobile devices, applications running in the cloud, or servers in your datacenter) don’t actually talk directly to authoritative DNS services, except in very rare cases. Instead, clients talk to recursive DNS services (also known as DNS resolvers) which find the correct authoritative answer for any DNS query. Route 53 Resolver is a recursive DNS service.
When receiving a query, a recursive DNS service like Route 53 Resolver may either be configured to automatically forward the query directly to a specific recursive DNS server, or it may recursively search beginning with the root of the domain and continuing until it finds the final answer. In either case, once an answer is found, the recursive DNS server may cache the answer for a period of time so it can answer subsequent queries for the same name more quickly in the future.