This was my first reaction as well. The keys use a unix timestamp, which are clearly not going to be synchronized by default so for event ordering purposes acro

This was my first reaction as well. The keys use a unix timestamp, which are clearly not going to be synchronized by default so for event ordering purposes across a distributed system this is dodgy. For providing better query locality it probably doesn't matter significantly though which seems to be the main benefit here while preserving the other benefits UUIDs provide.