5. Performance Optimizations
For optimal performance (i.e., minimum connection setup time), clients SHOULD implement a client-side DNS cache. Responses in the Additional section of a SVCB response SHOULD be placed in cache before performing any follow-up queries. With this behavior, and with conforming DNS servers, using SVCB does not add network latency to connection setup.
To improve performance when using a non-conforming recursive resolver, clients SHOULD issue speculative A and/or AAAA queries in parallel with each SVCB query, based on a predicted value of TargetName (see Section 10.2).
After a ServiceMode RRset is received, clients MAY try more than one option in parallel and MAY prefetch A and AAAA records for multiple TargetNames.