LuaJIT is such an amazing piece of software - apparently to such an extent that only Mike Pall fully understands some of its internals. Besides being much faster than the official Lua VM, it offers extended features like the FFI library [1].

Kong[2] uses it extensively, by leveraging the underlying OpenResty[3] framework.

[1] http://luajit.org/ext_ffi.html

[2] https://github.com/Mashape/kong

[3] https://github.com/openresty/lua-nginx-module