I do agree that Rails is often a cause of bad performance. Not in the first place because of its own, or Ruby's poor performance, but because it's easy to writ

I do agree that Rails is often a cause of bad performance. Not in the first place because of its own, or Ruby's poor performance, but because it's easy to write horrible code, and hard to write nice code in it. AR is a very leaky abstraction over a DB. A horrible query always a mere has_many, sort or default scope away. It's MVC horribly unsuited to manage and isolate business logic. The result often indeed being code that performs terrible.