Code is available at https://github.com/JeffreyRosselle/net-chat-application-azure-service-bus-topics-signalr

I’ll see if I can post the code somewhere. Depending on how you configure your code, you can indeed say that a topic is a group and subscription an user. But you could also create multiple groups in one topic and filter them out with the subscription filter. In the example above the subscription is set to get all messages. But if you use the subscription filter you could say that the topic is just a processor and the subscription is the group. Also multiple users can “subscribe” to the same subscription. So in the end you could subscribe all your 4.000 user to one “group chat”-subscription and then create a subscription for each 1:1 chat. Keep in mind though that you can only create 2.000 subscriptions, so you’ll have to delete every subscription when a chat ends. More info on the limitations can be found here: https://docs.microsoft.com/en-us/azure/service-bus-messaging/service-bus-quotas I think the standard 1 should be enough, but you should check out the Azure Calculator to see if stuff doens’t get to expensive for you: https://azure.microsoft.com/en-us/pricing/calculator/

My apologies Merrick, ServiceBusTopicHub should have been changed to ChatHub. This was error from my part since I forgot the edit the piece of code. Code has now been changed to correct name.