Our use case is that we have clients who need updates for a dynamic list of items with unknown (to the client) keys. Previous discussions on the topic with moderators have suggested the use of COMMAND mode, basing the structure around the stock demo. In that demo, however, there is always a list of items (keys) that are subscribed to. Our use case provides no such list. Is that really the right model, or is there a different model we should be following?