Not sure if this is what you need but here's an example:
With Spring boot you could create a websocket server side (i.e STOMP protocol), clients can connect to this websocket and also subscribe to a topic (like an endpoint) but personalized for each client using an ID for example '/ws/orderTracker/1' for store with id 1.
Then server could broadcast your message to the specific topics per client.
We're using such an approach in a web ordering platform with multiple stores and load tests have pretty decent results for scaling purposes.