Depending on the granularity of the notification target group, the application design can include a notification service; otherwise, another option would be to have a setup where the notification infrastructure can be integrated into either one of the existing services. For instance, if the application does not require a user-specific messaging scenario, there is no need to track device registrations. In this case, the client-side registration mechanism can be implemented so that notification categories are created and the backend services can send the notifications to target tags.
As part of our auctions application, let's use the following user story to start the implementation of our notification service:
"As a product owner, I would like to have a notification service created so that I can have an open channel to my user group through...