I'm building an SMS call and response system in a new app that receives a message via an aggregator gateway, checks it for functional keywords (run, stop, ask, etc), then processes it appropriately (save to the database, return an answer, or execute a task based on the users authorization). It's running fine at the moment as there are only a few users, but I figure its going to have more issues as we scale it up. We're currently running it on a single DV machine (mediatemple base dv).

My question is this: does it make more sense to set something up like Memcached to run a queue, or a simple database with a daemon running to process each message one by one? I don't have much experience with either, so any advice would be helpful. Since the messaging is somewhat time-sensitive, what would be the fastest and most reliable way to handle this?

Also, since we're sending responses, I'll probably need to set up and outbound message queue as well. Would it make sense to use the same concept for both?