I think it is worth it to try a simpler solution first. have a subscription for all of a users friends instead of a sub for each online friend. on the server you may want to use 2 lists per user for figuring out dispatch/rendering. a list of their friends, and a list of observers. maybe these 2 lists sound redundant, but you’ll be able to add a backoffice or followers without doing hacky stuff to the render list. when something changes with a user you iterate through the observers and dispatch status. if you get to the point where this kills your server then you can use something like a message queue for update dispatching, or use delays.
