>Amazon Aurora with MySQL compatibility is also built using MySQL https://aws.amazon.com/rds/mysql/what-is-mysql/
Tell me more about how uninformed I am...
Mysql won't even break a sweat for a few million records. I have run mysql databases with a single instance and billions of records with little optimization needed.
PostgreSQL is great for developers and I love some of the features it has that mysql doesn't (although mysql 8.0 has caught up quite a bit). But Postgresql is not nearly as battle tested for highly scaled implementations and in many cases will not perform as well as mysql.
I get the impression you have never actually built anything or you would know how so much of the internet runs on a php/mysql stack (think big, like Wikipedia).
And your comment about being zapped by 240v shows that you don't understand how electricity works. You could be zapped by 240v and barely feel it if you aren't grounded well. So to say you know what it is like to be zapped by 240v is like saying you know what it is like to get hit by a car. There are a million shades of grey of how that could end up.
