The document discusses the architecture of Wunderlist for Android. It describes how Wunderlist was redesigned with three independent layers - an Android layer, Sync layer, and SDK layer. The Sync layer manages business logic and sync operations using models, services, a cache, and a "Matryoshka" mechanism to resolve conflicts. The SDK layer provides APIs, models, and real-time sync via websockets. The Android layer focuses on decoupling the UI from business logic using MVP and loads data asynchronously from the Sync layer via EventBus and Loaders.