1st
it is doable for specific private relay based where only subscribed npubs are allowed and user has added relay to profile
not a mesh any<->any
2nd scalability
will depend on cpu/ram/net of above private club relay - it push 1million subscribers
people like LynAlden wooecomic other may find popular for huge paid base followers
Why do you need a private relay if the events themselves are encrypted? The idea is to push encrypted events to each receiver's own relay by simply subscribing to the author's feed.
thinking from standpoint of performance / scalability (yes it can be centralized like club relay)
if can push encrypted in "mesh of relays" only for subscribed npubs efficiently it can work too
You could probably do it if all subscribers are on same renewable schedule, you rotate keys when subscribers renew, and renewed subscribers get updated key to be able to decrypt. Otherwise you're trying to encrypt duplicate notes, one to each subscriber which is a lot of unnecessary data.
Yeah this would do it and be scalable. However, a user could share the key with a friend to grant access to the content. Dunno how much that would matter in practice.
