Nice article on rewriting something: it focuses on the need for the rewrite, and on an analysis done beforehand to get an idea of what to focus on. The rewrite is driven by a successful business, in other words.
I'm a bit curious what was so slow about the Ruby code, as it sounds like it was just doing 'managing' rather than actual heavy-duty processing, which no, it is not good at.
Erlang sounds like it would have been a good fit too, although it's not quite as performant as Go.
