You present very valid arguments. Regarding UUID v1, refer to spec in section 4.5. "Node IDs that Do Not Identify the Host". In the case of generating IDs, I d

You present very valid arguments. Regarding UUID v1, refer to spec in section 4.5. "Node IDs that Do Not Identify the Host". In the case of generating IDs, I don't care about the device's MAC or allowed block of addresses to use, so I can make a better use of that. Some implementations of UUID v1 uses random jitter which is what I believe is up to date and useful for this case. In some cases not allowing the number of bits is a hard constraint. In other cases you'd want to generate a TimeUUID (Cassandra) and take down 2 goals in one strike. Eventually, in the second part, I pick generating a TimeUUID with simple_uuid (which uses jitter, https://github.com/ryanking/simple_uuid/blob/master/lib/simple_uuid.rb#L56 https://github.com/ryanking/simple_uuid/blob/master/lib/simp...) exactly per your conclusion. The goal of this part of the post was to present the problems this kind of thing presents :)