"Only" 10k machines producing a combined 100 billion transactions per second is pretty hard to imagine, least of all that would all be producing transactions th

"Only" 10k machines producing a combined 100 billion transactions per second is pretty hard to imagine, least of all that would all be producing transactions that are part of the same namespace. Virtually all UUIDs are meaningless outside of a particular system in which they were created. There is a solution that doesn't require extending UUIDs (which has a storage cost everyone pays), which is to use a URI/URN instead of a UUID to provide a namespace. In practice this already occurs, except the namespace (scheme, path) containing the UUID is implicit, as it hasn't been named.