The package which provides a reactive and shared (between client and server side) subscription data context. When you subscribe to a publish endpoint, a reactive data context is established which can be read and changed both on the client or server side to provide alternative (reactive) way of passing arguments to the publish endpoint, without subscription restarting.
This is useful for alternative way of implementing infinite scroll where you can know both the number of all documents available on the server for the query, and also increase number of published documents without publication restarting and all documents publishing again.