128 bits is 16 bytes. BIGINT is a 64 bit int (long or long long). So there is at least additional storage required, and probably some CPU cost as well. And eve

128 bits is 16 bytes. BIGINT is a 64 bit int (long or long long). So there is at least additional storage required, and probably some CPU cost as well. And even UUIDv7 isn't guaranteed to produce sequential IDs, but it's probably good enough to not seriously fragment your table storage. But yes, UUIDs are usually stored as integers.