One major aspect of primary keys not mentioned in the article is the performance of queries. I did some benchmark recently, where serial (32 bits) was significa

One major aspect of primary keys not mentioned in the article is the performance of queries. I did some benchmark recently, where serial (32 bits) was significantly faster than the native Postgres UUID type. The worst scheme you can use is a string; if you encode something like ksuid as a plain string rather than an efficiently packed byte sequence, query performance becomes significantly worse. I didn't benchmark sorting, but I assume it's similarly impacted.