When using the incrementing key pattern you increment the count every time you add a new document and use count in the key of the document.
What if you remove a user? You can’t decrement the key and if you did you’d have to update all existing keys in the bucket to reflect the new structure.
So in this case would you keep all the old users and determine if they are “offline” or “deleted” when you iterate over them all in this case? And how would then use the count to actually determine how many “active” users you have in your bucket. You’d have to use a view at that point.
I’d love some insight on this subject. I really find the data modeling patterns very interesting.