It's going to depend on the database. This article is primarily focused on InnoDB and goes over the read/write locality issues with a uuid. That isn't always g

It's going to depend on the database. This article is primarily focused on InnoDB and goes over the read/write locality issues with a uuid. That isn't always going to matter (or can be a very good thing). For a KV store like dynamodb a uuid is a great key because it'll distribute nicely across your shards. It also depends a lot on your query patterns. If you have a uuid primary key but you're partitioning by some other value you may end up significantly reducing the number of pages you have to look through.