[kevingadd]

Probably poorly by default, but you could use a hash of the uuid as a key (to try and more evenly spread the entropy) or key it off a suffix instead of a prefix since iirc that's where most of the entropy lives.

In practice if you want good performance and scalability it's important to select keys well.

[hobs]

For this use case people generally choose sequential UUIDs or they want random ones to prevent hot pages for their inserts.