When configured with an external LDAP authentication & authorization, mongod typically performs three LDAP queries using the separate TCP connections:

1. userToDNMapping processing
2. to check the provided password
3. groups retrieval

The proposed solution is to maintain the connection pool to the external LDAP server and reuse those connections to authenticate the MongoDB clients.

The authentication state of a connection needs to be set back to unauthenticated (using an anonymous bind) before the connection will be returned back to the pool.