Spanner in particular wants random primary keys. But there are sharded DBMSes that still use sequential PKs, like Citus. There are also some use cases for semi-sequential PKs like uuid7.
What about spanner specifically benefits from random ids over sequential ones?
I'm not an expert on Spanner, supposedly it's due to hotspotting. Your data is partitioned by primary key, and if you make that sequential, all new writes will hit the same master. https://docs.cloud.google.com/spanner/docs/schema-and-data-m... explicitly recommends a uuid4 or some other options
That's another thing, some say to use uuid7 for sharded DBs, but this is a serious counterexample.