By now, we've all written JSON APIs in Rails. But how do you write fast, testable and sane APIs? I'll guide you through the trials of designing and building awesome, scalable APIs. We'll cover Rails-API, ActiveModel::Serializers, and all the heavenly goodness our ecosystem has to offer. We'll muse upon the approaches to authentication, ensuring we remain good REST/HTTP citizens and maybe if we have time I'll share some of my top secret beard grooming tips.