X.509
MongoDB supports X.509 certificate authentication for client authentication and internal authentication of the members of replica sets and sharded clusters. x.509 certificate authentication requires a secure TLS/SSL connection. For more info, please consult https://docs.mongodb.com/manual/core/security-x.509/ and https://docs.mongodb.com/manual/tutorial/configure-x509-client-authentication/#authenticate-with-a-x-509-certificate