Cloud Foundry is mostly written in Ruby and Go. New components are generally written in Go and several Ruby parts are being progressively replaced by Go parts

Cloud Foundry is mostly written in Ruby and Go. New components are generally written in Go and several Ruby parts are being progressively replaced by Go parts (especially Diego). Pivotal (my employers) sold $40 million of PCF in the first year of sales. So it's got a bit of traction here and there.