Heroku makes the most sense if you aren't running your app and your database on the same server. It's particularly easy to scale if your app doesn't contain an

Heroku makes the most sense if you aren't running your app and your database on the same server. It's particularly easy to scale if your app doesn't contain any state in and of itself - just spin up a few copies that point to your database (which you can also scale up with a paid provider like MongoHQ). For an example, I have a single-server app running on Rackspace with a same-server MongoDB. I pushed the web app to Heroku, now all I need to do is set up a connection to MongoDb (either via MongoHQ at $20-50/mo or with a hand-secured connection back to my existing database) and now I can stop worrying about Nginx and Apache and whatnot. If my load grows I can spin up extra web server instances or increase the resources allocated to my DB server.