>Why do you think it's a UUID?
Because of this:
>Also notice that we are not using serial keys; instead, we are using varchar(50), which stores client-generated GUID values
Because of this:
>Also notice that we are not using serial keys; instead, we are using varchar(50), which stores client-generated GUID values
As long as it meets the statistical properties for collision, I don't see any problems with making a 50-bytes GUID. The essential thing is the statistical property, not the number of bits.
Like I mentioned, there are different UUID/GUID schemes using more than 128 bits publicly available already. You don't have to invent one. They may simply be using one of those with additional bytes reserved for future algorithmic changes (using first few bytes as a header to specify the algorithm).