mruby is the lightweight implementation of the Ruby language and was released about a year ago. Can we use mruby to write web services?
This answer is YES - our company used mruby in large scaled web services. Even with mruby, we were able to create web services with tests and gems, and it also helped to solve some problems using Ruby code outside of a Rails application. In essence, mruby also provides programming features like HTTP to us web programmers.