Why Nginx Doesn't Implement FastCGI Multiplexing?

[momyc]

Another scenario. Consider application that takes few seconds to process
single request. In non-multiplexing mode we're still limited to roughly 32K
simultaneous requests even though we could install enough backend servers to
handle 64K such requests per second.

Now, imagine we can use FastCGI connection multiplexing. It could be just
single connection per backend. And, again, we are able to serve roughly
twice as many requests per second with the same hardware but little tiny
feature called FastCGI connection multiplexing.

Posted at Nginx Forum: http://forum.nginx.org/read.php?2,237158,241043#msg-241043