Response Queues - Scalability Concerns

“We need to create separate Response Queues for each subscribed client”. Dropbox has ~500M clients. Isn’t it a scalability issue to create, support, and manage 500M queues? How would that even look like if I were to use cloud platforms like AWS?


I also had the same question, how can we create requests queues like this for each account each client. That may not scale(AWS may be can do it) but still managing so many queues is hard.
May be some SNS topic or streams where each client can read the same message. but then we need to take care of expiration of the message, what if the client sync after 1 year, how will server convey lost response or updates?

Completely agree, it would be great to get clarification on this. Is there concept of dynamic queues at all allocated to separate users each?

Maybe they’re using some sort of message brokers (pub-sub) ? and not queues