If it is so common as you claim, could you point us to some public examples of this? I have never ever been concerned about concurrency in Ruby, or Python or P

If it is so common as you claim, could you point us to some public examples of this? I have never ever been concerned about concurrency in Ruby, or Python or PHP. Just deployed the number of workers which would be able to serve our peaks. I do write high concurrency application though, but those are not web apps and are not written in these languages.