A while ago when I started my first job in LA, I was using MSSQL. I was told to never use count(), and rather to use count(1). Several people insisted this performs better than count(), and since I really didn’t care to argue or look into it, I just started doing it.
Fast forward to today, where I am still writing count(1), but on MySQL. I’m at a different company now, but working with a lot of the same people.