Parse is a BaaS for mobile developers that is built entirely on AWS. With over 150,000 mobile apps hosted on Parse, the stability of the platform is our primary concern, but it coexists with rapid growth and a demanding release schedule. This session is a technical discussion of the current architecture and the design decisions that went in to scaling the platform rapidly and robustly over the past year and a half. We talk about some of the lessons learned managing and scaling MongoDB, Cassandra, Redis, and MySQL in the cloud. We also discuss how Parse went from launching individual instances using chef to managing clusters of hosts with Auto Scaling groups, with instance discovery and registry handled by ZooKeeper, thus enabling us to manage vastly larger sets of services with fewer human resources. This session is useful to anyone who is trying to scale up from startup to established platform without sacrificing agility.