If you want to handle 1M connections, you can tune this. It will probably be the easiest thing to tune of many. Note that 1M connections terminated stud/hitch is actually 3M sockets: 1M inbound to stud, 1M initiated by stud and 1M terminated by your underlying server. That's a lot of connections on localhost (on the plus side, 127.0.0.1 is a /8)