Early on, the author says: "If you write an application with Rails, you probably have to write a whole bunch of new code, or at least change around all of your

Early on, the author says: "If you write an application with Rails, you probably have to write a whole bunch of new code, or at least change around all of your old code, in order to get it to run on multiple computers." This is absolutely true. Rails "scales" by forcing programmers to do a whole lot of extra work (yes, sharding and secondary databases and lots of other things) which isn't particularly natural in the framework. As a programmer, I'm not particularly thrilled to have to set up and maintain a memcached cluster and then write code to make sure my object reads pass through the caching layer. It's more work. It's more fragile. It probably forced me to revisit and modify working code. The author wants to build a framework where scalable code is the default and natural way to write applications. Seems pretty well-thought out. He touches on many of the common pain points.