Not new idea to use lua in the db, but if you wish more use lua in the project. I recommend to see http://tarantool.org instead redis with lua.
Op here! One of the primary reasons for using Redis here is not so we can use Lua (even if it is great!) - it's so that we can generate IDs using a service we already have. This idea could be extended to anything that allows user scriptable behaviour - for example, we know at least Instagram are doing this using PostgreSQL stored procedures.