This is essentially what these PaaS services do. Appfog for example gives you 2GB of ram to deploy your app with for free. You can deploy an app to 8 separate instances with 256MB of ram, or you can adjust it differently. With heroku you get 1 "dyno" for free, and for each additional dyno it's another charge, etc. etc. They do all the work of load balancing and making it "just work"