The application I'm interested in is a log-based artifact registry. Volume would be very low. Much more important is the immutability and durability of the log.

I was thinking that writes could be indexed/prefixed into timestamp buckets according to the clients local time. This can't be trusted, of course. But the application consumers could detect and reject any writes whose upload timestamp exceeds a fixed delta from the timestamp bucket it was uploaded to. That allows for arbitrary seeking to any point on the log.