That's one way to look at it. Another is when this app started 3.5 years ago, Rails & the app had a drastically different performance profile and Amazon didn't

That's one way to look at it. Another is when this app started 3.5 years ago, Rails & the app had a drastically different performance profile and Amazon didn't have super-over-subscribed hardware. Not that it matters much, but there's nothing convenient about having to engineer around EC2. And doubling your capacity or constantly upgrading instance sizes is not cheap, nor a scalable solution in any practical sense. Pick your language though. With terrible forking performance, any process-based execution environment is going to have similar issues. And I found running a servlet container on anything smaller than an m1.large to be an utter waste. 1.7 GB RAM isn't enough for many JVM-based apps and threading could easily overwhelm the system. Anything less than high I/O capacity just can't keep up.