Birds of a Fiber: A look at Falcon, a modern asynchronous web server for Ruby
The GitHub Readme describes Falcon as, "... *a multi-process, multi-fiber rack-compatible HTTP server ... Each request is executed within a lightweight fiber and can block on up-stream requests without stalling the entire server process." The gist: Falcon aims to increase throughput of web applications by using Ruby’s Fibers to be able to continue serving requests while other requests are waiting on IO (ActiveRecord queries, network requests, file read/write, etc).