I think this could be a nice book for advanced programmers.
I could be a state of art about scaling ruby.
Starting with an overview of bottlenecks and then moving through different way to scale ruby apps:
* How to write fast ruby (as we all know there are real performance differences between two syntax, but it is much dependent of the VM)
* Choosing a VM (depending of the goals, and features we want to support)
* Non blocking IO
* Event driven … * Distributed Ruby
And many things i’ve forgot.