fairy is a framework for distributed processing in Ruby, originally designed at Rakuten Institute of Technology with Yukihiro Matsumoto, the founder of Ruby. Although fairy was inspired by MapReduce model, a well-known programming model for distributed processing, it's more flexible and suitable for wider use. That's due to fairy's programming model, called filter IF, and various built-in filters. fairy is implemented in Ruby and inherits its high productivity and simplicity. fairy's API is quite similar to Ruby. Therefore most programmers who know Ruby can easily understand and use it.