why do you say this architecture can handle millions of users?
#ditto is the best kept secret on nostr. If you want to try an amazing client, go to:
Or install your own version using:
https://docs.soapbox.pub/ditto/install
With an elegant, scalable architecture which can handle millions of users. This was the missing piece of the puzzle that nostr has needed.

Discussion
Alex has built and delivered things to millions of users before, as have I. I see good design patterns in there. I may be wrong on that, but this is the first thing I've seen in the space that I think has a really good chance of scaling. If someone else does it first, so much the better.