I have previously also used a network library for SCGI, and some homegrown code which I can't remember.
I should point out that I am planning to move away from Lua for my webapps so that others can maintain them if that is needed. My plan is to use server-side Javascript built on V8 (Google). I still prefer Lua - but Javascript programmers are pretty easy to find.
I have been using Lua for almost 2 years now for web applications. Speed has never been an issue for my particular application (relatively small scale online research) - and I've often just been using old fashioned CGI technology.
My only negative comment about the experience would be that I tend to accumulate some C extensions which take a little effort to deploy when you move servers.
I have previously also used a network library for SCGI, and some homegrown code which I can't remember.
I should point out that I am planning to move away from Lua for my webapps so that others can maintain them if that is needed. My plan is to use server-side Javascript built on V8 (Google). I still prefer Lua - but Javascript programmers are pretty easy to find.