# Federated Subscriptions with Router's HTTP Callback Protocol

DevFeed: [Federated Subscriptions with Router's HTTP Callback Protocol](<https://devfeed.tech/articles/federated-subscriptions-with-router-s-http-callback-protocol-23301.md>)

Original publisher: [Read original article](<https://www.apollographql.com/blog/federated-subscriptions-with-routers-http-callback-protocol>)

Author: Liz Hennessy

Published: 2024-04-30T09:17:00Z

Content type: tutorial

Language: en

Sources: [Apollo Blog](<https://devfeed.tech/sources/apollo-blog.md>)

Topics: [GraphOS](<https://devfeed.tech/topics/graphos.md>), [real-time](<https://devfeed.tech/topics/real-time.md>), [WebSocket](<https://devfeed.tech/topics/websocket.md>), [HTTP](<https://devfeed.tech/topics/http.md>)

Tags: [backend](<https://devfeed.tech/tags/backend.md>), [graphos](<https://devfeed.tech/tags/graphos.md>), [http](<https://devfeed.tech/tags/http.md>), [real-time](<https://devfeed.tech/tags/real-time.md>), [subscription](<https://devfeed.tech/tags/subscription.md>), [subscriptions](<https://devfeed.tech/tags/subscriptions.md>), [websocket](<https://devfeed.tech/tags/websocket.md>)

## AI overview

This tutorial explains how federated subscriptions in GraphOS use the Apollo Router's HTTP callback protocol to deliver real-time updates from subgraphs. It contrasts callback-based communication with WebSockets and demonstrates a subscription that retrieves stock data from multiple services.

## Source excerpt

Federated subscriptions through GraphOS make the path to real-time data much smoother: a single query delivers continuous updates while the Apollo Router coordinates behind-the-scenes operations to subgraphs. In addition to enabling subscriptions via WebSockets, the router supports an HTTP callback-based protocol. With callbacks, the router can communicate with subgraphs without needing to maintain multiple persistent connections for each new subscription event.