> Aside from the data locality, I still find the programming model (a globally-unique and addressable single-threaded class instance) to be quite nice, and would want to emulate it even without the Cloudflare edge magic.

You might be interested in Plane (https://plane.dev/ / https://github.com/jamsocket/plane), which we sometimes describe as a sort of Durable Object-like abstraction that can run anywhere containers can.

(I'm also one of the articles you linked, thanks for the shoutout!)

It's the actor model essentially.

You can have a DO proxy each user connection, then they forward messages to the multipler document. The user proxy deals with ordering and buffering their connection message state in the presence of disconnects, and the document DO handles the shared state.