Cross-platform push notifications that can engage your customers even when your app is in the background are becoming a central part of a mobile app user experience. Some customers may rarely open an app that provides useful information to them; for them, the notifications are the most important part. But great user experiences can break if your messages get dropped or delayed. How do you ensure your messages are delivered fast and reliably at scale? And how can you use them to extend the user experience of your app? In this session, we show you how Amazon SNS provides the performance and simplicity of a managed service, while also supporting interactive notifications, silent push, and broadcasts to large groups. We also learn from Mailbox, who rely on large-scale push notifications as a core part of the user experience, and who will share real-world design patterns.