Part 3 of the User Connectivity Architecture series. Introduction The first post in this series described the pattern: a heartbeat on a timer, an Event Hub, a worker writing sessions into Redis, and Redis key expiration driving facility online/offline status. One detail matters later. The heartbeat interval is not hard-coded in the client. The API tells the client when to call next, and the default is 30 seconds. The second post covered two years of running that in product...