I wonder how keys are assigned to rows and how the adjudicator is shared.

The author also mentions a leader adjudicator, which means there is probably some sort of coordination to pick a leader. This raises the question of how a leader is picked, and if leadership changes based on how hot a key is in a given AZ.

This blog series is a great read. Every day Marc drops excellent content and leaves room for questions, which he ends up answering on the following days. Hope more details come next.