I am using nginx along with php-fpm to server a busy mysql-based site.
Currently I am using
keepalive_timeout = 5, however I have no clear idea about how to optimally adjust it. So appreciate your hints.
What do you need to adjust it to do, or rather: are you seeing any problems with having it set how you do?
There isn't a good one-size-fits-all answer; if most client browsers are able to load all the resources on a page in 5 seconds then 5 seconds is just fine, but it completely depends on your application's needs - if your nginx server were serving as a reverse proxy for Exchange ActiveSync, for instance, you'd want it cranked all the way up to half an hour.