The "naive" thing in Ruby, if you're serving HTTP requests, is to use some kind of app gateway that allows concurrency, such as puma or unicorn. It's just not all that viable to do something more basic than that unless you're willing to write all the request handling stuff by hand.

That aside, a ruby script that can't handle 20 req/s on 2 vcpus seems rather suspect. I'd be really curious what that code looked like. I'm doubtful that it has much to do with the language and not the code design.