I have spent four years running WordPress at scale on Altis Cloud. I expected the lessons to be about infrastructure. Looking back, they were just good engineering habits.
Assumptions are dangerous, better to seek the data to prove them, even the obvious ones. Unglamorous work pays off when things break. Willingness to understand beyond what you strictly need to know puts you in a better position to make informed decisions.
The talk walks through actual experience and incidents and how each one taught me one of these. Useful for anyone who works on WordPress sites of any size.