There's no single self-contained solution in the post really, it's more an illustration of a number of useful things that Lua can be used for. I might try to put another post together at some stage though.

For us our main goal is to prevent the majority of requests from even reaching the Rails stack. We've done this by introducing full page caching across the site, for both logged in and logged out users. This means that only a small percentage of requests at peak times need to touch Rails or any database at all - everything is served by Nginx.

This hasn't been without its challenges. The last section of this post might give a clue as to how we've solved the most difficult ones. I will think about a post tackling this whole subject but I need to think about how to get it across, it's not easy.