See https://github.com/alebsack/rack-fiber_pool/blob/master/example/app.rb rack-fiber_pool https://github.com/alebsack/rack-fiber_pool https://github.com/mperham/rack-fiber_pool/ A Rack middleware component which runs each request in a Fiber from a pool of Fibers. You need a EventMachine-based server (e.g. thin or rainbows) Based on FiberPool https://github.com/JonRowe/FiberPool An implementation of a fiber pool that can be used to cooperatively schedule workloads. Best used in combination with EventMachine to allow multiple workloads to be processed at the same time. http://rubylearning.com/blog/a-quick-introduction-to-rack/ by Satish Salim