Scan needs to go to the threads that contain the keys you want to scan.

The iterator should live in the client, rust has an AsyncIter only in nightly, so I would probably implement a trait that has a next function that the user needs to call manually, like I did in iter_filter.

To make this performant you would probably need to implement a new response type that streams the results from the server, instead of closing after a single response.

Not a simple feature, but it basically comes down to this.