Not a YC company, but Square was also founded on Ruby. There was a pretty large monolithic Rails app that AFIK, may still exist. Though we hired a bunch of peo

Not a YC company, but Square was also founded on Ruby. There was a pretty large monolithic Rails app that AFIK, may still exist. Though we hired a bunch of people from Google, who brought Java, and we went hard towards SOA. Around 2013 there was a Java vs Ruby war in engineering, with many upset people. It ended in peaceful coexistence. But most things in the main payment flow ended up Java.