First of all, this thread contains a lot of information! I'm in the process of implementing something similar and it has helped me a ton.

I was just wondering, as long as you're using Lua anyway, why not do away with Drizzle completely, and just make Lua connect to the database to retrieve the correct URL? Is it because Drizzle will keep one connection to the database per nginx-instance, so there is less overhead, compared to Lua which would have to connect and disconnect to the database for every request?