Federated subscriptions in GraphOS provide a scalable solution for real-time data at scale, addressing the challenges of traditional microservice architectures and REST. By introducing a new transport protocol, WebSocket deduplication, and updated query planning, federated subscriptions enable a single subscription to serve data from multiple separate services, improving performance and reliability for infrastructure teams. This approach allows feature developers to build with data that lives across dozens or even hundreds of separate services using a single subscription, reducing the need for lockstep coordination across backend teams. With federated subscriptions, clients can use a single subscription to access the appropriate data, while backend teams can contribute fields from real-time data sources without tight coupling across teams. The new protocol for client-to-router communication and deduplication mechanism significantly reduce the work required for app developers to use federated subscriptions, making it easier to deliver real-time API infrastructure at scale.