When running Lua, always consider running it on the LuaJIT (http://luajit.org/). It's extremely fast, portable and lightweight JIT compiler for Lua, although it only supports Lua 5.1.

The performance improvements are incredible, and it allows you to write inline C code thanks to the FFI library (declaring it like this https://github.com/Mashape/kong/blob/master/kong/plugins/fil..., and invoking it like this https://github.com/Mashape/kong/blob/master/kong/plugins/fil...)