DRIVERS-1983 : Implementation notes for drivers: Drivers must update their load balancer test runs in Evergreen to run on "latest", and then may choose to use 5.2.0 GA and higher for the runs when available. Drivers must remove the use of service ID mocking (e.g. FAKE_MONGODB_SERVICE_ID ) in their code. Drivers must set the  LOAD_BALANCER  environment variable to "true" in their load balancer test runs and pass the environment variable when invoking run-orchestration.sh . Drivers may need to make changes to their test runners if they had direct connections to the mongos in their tests with the "loadBalanced=true" URI option set. (Such as utility clients - they must go through the load balancer now in these cases.) See:  https://github.com/mongodb-labs/drivers-evergreen-tools/pull/183 See:  https://github.com/mongodb/node-mongodb-native/pull/3089