Earlier quoted context omitted.
I'm working on a web service (build on top of Scala and the JVM) that's handling between 1500 and 3000 reqs per second per c1.medium instance, with an average time per request of under 15ms. This is real traffic, with the web service receiving between 16,000 and 30,000 total requests per second during the day. A c1.xlarge can do 7000 reqs per second or even more, but for the moment I felt like the difference in prici…
I just wanted to add -- since you're not the first to point out the Rails part -- that I've also run a 42 node Cassandra cluster on a m1.xlarges and did a fair bit of CPU-bound operations (encryption and compression) on hundreds of TB of data on cc2.8xlarge. I just used the Rails one as an example. In the case of Cassandra, disk I/O was a constant issue. So, we grew the cluster much larger than would be necessary on…
Unfortunately we also need auto-scaling capabilities and map-reducers and stuff. Maybe Google's new "Compute Engine" service will prove to be better.