What to read to systematize and supplement knowledge about MySQL?

Question

MySQL

Good day to all.
I have been doing web development for a long time, using php + mysql, etc. I know how to build queries, I know how to use join, I used having a couple of times in interviews. I know a little about the differences between myisam and innodb, I have a little idea about procedures and heard about triggers from the corner of my ear.
Most of my work with MySQL was limited to writing queries.
I understand that you need to pull up a lot of points, so I ask for advice. Why read about MySQL in order to delve into indexes, procedures, etc., to systematize and streamline current knowledge, but not to delve into biographies of MySQL developers and too low-level logic?
And at the same time, it would probably be nice to read something similar for PostgreSQL.

Answer 1

Schwartz B., Zaitsev P., Tkachenko V. et al. - MySQL. Performance optimization

Answer 2

the official documentation for both MySQL and PostgreSQL is very detailed... read it.