Limits and pricing
The Real-time Updates API is capable of supporting hundreds of thousands of concurrent connections.
Technical Limits
Every plan comes with a technical limit of a maximum of 500 concurrent connections per project. This means, at the same time, that there can be a maximum of 500 open SSE connections to the same project. If you need more, please contact us so we can discuss your needs and see how we can help you scale.
Pricing
Even though the Real-time Updates API is not billed per se, it uses the Content Delivery API to function, so it contributes to the number of API calls to it.
What makes the cost predictable is that CDA usage is independent of the number of connected clients. Clients that open an identical subscription request are served by a single shared re-fetch. Whether 1 or 500 clients are watching, a content change triggers the same single CDA request, and every client receives the update.
A few consequences follow from this model:
One request per relevant change. Each content change that affects a query's result triggers exactly one CDA request for that query.
Irrelevant changes are free. Edits elsewhere in the project that don't affect a query's result trigger no re-fetch, and therefore no CDA request, for that query.
Usage scales with distinct subscriptions, not clients. Subscriptions are grouped together only when their requests match exactly; any difference — in the query, its variables, or any other request detail — makes them count separately, each with its own re-fetch. Your CDA usage therefore grows with the number of distinct subscriptions being watched, not with the number of connected clients.
Example
Imagine 500 visitors viewing the same homepage, all subscribed to the same hardcoded query, with content changing every 30 seconds.
Because every visitor shares the same query, they are served by a single re-fetch. Each change produces one CDA request, so a change every 30 seconds results in 2 CDA requests per minute in total — regardless of the 500 connected clients.
By contrast, if those same 500 visitors each subscribed to a different query, a single homepage change could trigger up to 500 re-fetches — one per unique query — because there is no longer anything to share.