not that i'm aware of. the big thing that spanner gives you that zanzibar uses is the ability to kind-of-linearize transactions in a distributed system using its TrueTime API. you only have that problem in a distributed system, so you don't see it in postgres or mysql at all. cockroach solves it a different way - they've got a pretty good writeup of it here: https://www.cockroachlabs.com/blog/living-without-atomic-clocks/, and to my knowledge there isn't a meaningful performance difference between spanner and cockroach. i'd let the devs weigh in there though.