Knock offers a flexible notifications infrastructure for developers to manage in-app and out-of-app notifications without custom application code. The company focuses on in-app notifications, which are crucial for reducing notification overload and enhancing long-term user retention by providing a centralized place for users to view and act on notifications without switching applications. Knock supports three primary types of in-app notifications: inboxes, feeds, and toasts, each serving different purposes based on the product's needs. The implementation of in-app notifications involves building both front-end and back-end systems to handle user interactions and real-time updates. Knock simplifies this process by offering ready-to-use components and services that integrate real-time inboxes, notification feeds, and toasts, while also allowing orchestration across multiple channels. The service is scalable, reliable, and includes observability tools to monitor system performance, providing a hassle-free solution to manage notifications efficiently.