Also mentioned on HN https://news.ycombinator.com/item?id=45323008
1. Users - your users table may not benefit by being ordered by created_at ( or uuid7 ) index because whether or not you need to query that data is tied to the users activity rather than when they first on-boarded.
2 Orders - The majority of your queries on recent orders or historical reporting type query which should benefit for a created_at ( or uuidv7 ) index.
Obviously the argument is then you're leaking data in the key, but my personal take is this is over stated. You might not want to tell people how old a User is, but you're pretty much always going to tell them how old an Order is.
There's also a hot spot problem with databases. That's the performance problem with autoincrement integers. If you are always writing to the same page on disk, then every write has to lock the same page.
Uuidv7 is a trade off between a messy b-tree (page splits) and a write page hot spot (latch contention). It's always on the right side of the b-tree, but it's spread out more to avoid hot spots.
That still doesn't mean you should always use v7. It does reversibly encode a timestamp, and it could be used to determine the rate that ids are generated (analogous to the German tank problem). If the uuidv7 is monotonic, then it's worse for this issue.