At least in the case of Postgres, I know from reading the source before that it stores UUIDs as 128-bit values and does optimized binary comparator operations o

At least in the case of Postgres, I know from reading the source before that it stores UUIDs as 128-bit values and does optimized binary comparator operations on those values. It can export and import UUIDs as text strings but does not treat them as text internally. I'm not sure why any competently engineered database engine would do otherwise.