Federated subscriptions with HTTP callback support are now available in Apollo Router, reducing real-time cloud spend and improving efficiency at scale. This feature solves the backend WebSocket problem, allowing for more flexibility and interoperability between the router and underlying services. With HTTP callbacks, the router no longer manages a WebSocket connection with subgraphs, making it suitable for serverless infrastructures. To use federated subscriptions with self-hosted instances of Apollo Router, users need an active Apollo GraphOS Enterprise plan, a federated GraphQL API with HTTP callback-compatible servers, and the latest version of Apollo Client with HTTP-based subscriptions support. The feature is now available in general availability (GA) release of Apollo Router 1.37.