It's an intermediate-level article, which means half-right and half-wrong. The GUIDs paragraph is mostly wrong. - there are a few different layouts for GUIDs,

It's an intermediate-level article, which means half-right and half-wrong. The GUIDs paragraph is mostly wrong. - there are a few different layouts for GUIDs, depending on need - MySQL int is 4 bytes, bigint is 8 bytes, guids are 16 bytes. Space is important in schemas, more than you know. - if you're not using SSD, then GUIDs will write slowly since they are random, thus causing seeks - GUIDs however are useful when you need an id that is visible to the user, since they're not sequential.