I feel like there should be a correction to the article. Ruby in JRuby is multithreaded. JRuby is not the most popular vm for Ruby, so I would most likely say that Ruby is not multithreaded. This is due to the GIL blocking access in the vm, where in JRuby the jvm is able to spin up threads for the language. The article here : http://stackoverflow.com/questions/56087/does-ruby-have-real-multithreading is 5 years old, but it explains more of the reason that Ruby MRI not being multithreaded. Now can the web server handle multiple threads? Sure, but it can in Nodejs as well. You are better off in other languages for CPU bound work.