The default behavior of SDAM when connecting to a replica set involves discovering the full cluster topology, then establishing monitoring connections to each discovered host.

For multi-region replica sets, there can be applications deployed to certain regions that may not want any cross region traffic, and replica set tags and other read preference configurations may be insufficient for guaranteeing this restrictions are fully enforced.

Given a PSS-SS-SS-SS style configuration across 4 regions, we should be able to define a connection string such as mongodb://host4:port,host5:port/?serverDiscovery=false where only the replica set members in the seed list are used for SDAM - as in though the full topology would be known, connection pools and monitoring/rtt connections would only target the requested hosts.