Knock has introduced a new Subscriptions API that allows users to efficiently notify large groups by modeling lists of subscribers, which can be notified through a single API call. This feature is designed to enhance alerting use cases, publish/subscribe models, and dynamic follower systems by offloading the responsibility of determining notification recipients to Knock. The API supports nested object hierarchies, enabling complex resource structures such as teams with multiple projects and project members, and allows for storing custom properties about user-object relationships. Currently, there is no limit on the number of subscribers or recipients that can be stored, and there is no additional cost for creating subscriptions. The Subscriptions API is available across all Knock plans, and users can begin implementation by consulting the provided documentation and reference guides.