At a previous company, we got burned using UUIDs as MySQL PKs. Turns out MySQL keeps data on disk sorted in PK order, so even a moderate INSERT workload would l

At a previous company, we got burned using UUIDs as MySQL PKs. Turns out MySQL keeps data on disk sorted in PK order, so even a moderate INSERT workload would lead to lots IO and disk thrashing as pages kept needing to be rewritten. Fun times...