An article promising to be quite technical demonstrates early on the author's inability to get their head around the spelling of the possessive form of "its".

An article promising to be quite technical demonstrates early on the author's inability to get their head around the spelling of the possessive form of "its". (Perhaps it's just me that finds this an unsettling juxtaposition. The About page wasn't useful in identifying native writer status.) Then we dive into some mistruths about emails being unique per user (I know plenty of people who still share email addresses, both personal and also in shared commercial accounts). I worked at a place a few years ago that had designed their entire accounts system around the idea of email addresses being immutable. They'd subsequently had to introduce a secondary column for actual email addresses -- customers would login with their historical email address as their ID. The idea that a uid is a 'natural key' just seems perverse (or at least demonstrates a profound misunderstanding of what a natural key is). A sideways reference - without actually using the phrase - to CAP theorem. Composite keys are suggested as a solution to a vaguely phrased problem without acknowledging the performance issues, and subsequent design constraints, they introduce. Ultimately there seems to be a misunderstanding about the differences between a (primary) key and an index.