The first version of Instagram for Android was built in four months by a team of two engineers. It’s been four years since that launch, and in that time we’ve added features such as video, direct messaging, photo maps, advertiser support. We’ve regularly released new filters, editing tools, and apps to unlock creative potential. Almost 30 engineers now work in our Android codebase every day. All this — yet Instagram for Android is still a fast-starting app and is only a 16MB APK download for most users. We will talk about how our app's architecture involved as the team grows, to achieve our performance and reliability goals.