MongoDB version 4.4 introduces support for TCP Fast Open (TCO) connections. For this to work, it must be supported by the operating system hosting MongoDB. The following configuration file (and command line) parameters have been added to enable and control support under the setParameter configuration option: tcpFastOpenServer, tcpFastOpenClient, and tcpFastQueueSize. In addition, four new TCO-related information counters have been added to the output of the serverStatus() database command.
You can refer to https://tools.ietf.org/html/rfc7413 for more details on TCO. For more information on the parameter, you can refer to https://docs.mongodb.com/master/reference/parameters/#param.tcpFastOpenServer. Refer to https://docs.mongodb.com/master/reference/command/serverStatus/#serverstatus for more information on serverStatus.
