This is the first of a series of posts describing the AppHarbor architecture. This post outlines the overall runtime layout.
AppHarbor currently runs on top of Amazon Web Services. This gives us access to lots of high-performance hardware, including fast SANs and excellent long-term storage. AppHarbor can quickly add more server-capacity on-the-fly as our users requirements change.
AppHarbor runs open source load-balancers that distribute load to multiple IIS based webservers. We can easily deploy single websites to many servers to distribute load and provide failover should a webserver go down. Indeed, the main appharbor.com site already runs in this configuration -- we just haven't opened up the necessary configuration option to users yet.
On the backend, we provide access to your choice of highly tuned shared Microsoft SQL Server instances or Amazon-maintained MySQL Relational Database Services. We are working on adding dedicated database instances for users requiring guaranteed database performance (if you need this right now, drop us a line at firstname.lastname@example.org and we'll work something out).
We're still working on a good pricing structure -- expect a preliminary pricing page very soon.