Universally Unique IDentifiers (UUID)
ietf.org
This specification defines the UUIDs (Universally Unique IDentifiers) and the UUID Uniform Resource Name (URN) namespace. UUIDs are also known as GUIDs (Globally Unique IDentifiers). A UUID is 128 bits long and is intended to guarantee uniqueness across space and time. UUIDs were originally used in the Apollo Network Computing System and later in the Open Software Foundation's (OSF) Distributed Computing Environment (DCE), and then in Microsoft Windows platforms.
This draft spec was eventually published as RFC 9562. Compared to the previous spec it adds versions 6, 7, and 8, plus best practices guidance.
Basically, there are a bunch of UUID alternatives that arose to fix the problem that UUIDs are bad for use as database keys in large tables (here’s the perspective of MySQL experts Percona). A bunch of these alternatives are actually linked from the RFC, which I haven’t seen done before. Version 7, in particular, is meant to address this use case.