This weeks outage asks an interesting question regarding hosting providers such as heroku with their "rock-solid ruby platform". I've always taken part of their offering to be that I don't have to think about infrastructure beyond the abstraction that they provide. Perhaps incorrectly I've been under the impression that paying for their service means they will worry about things like redundancy across availability zones or regions leaving me free to just build the app.

I'm a huge fan of heroku so I'm really just trying to clarify, are these services offering to take care of my infrastructure requirements or do I need to think about adding redundancy/failover etc. myself?

edit: http://www.heroku.com/how/architecture#routing-mesh is what set my expectations.