During the first few months of my first professional development role, I had a really odd bug on a live WordPress site that I couldn't replicate locally, despite having the same code and dependency setup. Using WordPress was a mistake but not the one I'm writing about.

I decided to copy live site and its database. Then I thought it best to delete all the users from the copy of the database (I'm not sure why I thought I should do that) and I did so via the WordPress admin UI.

What I wasn't aware of was there was a custom function to email the user before they get deleted.

I got inundated with hundreds of confused/angry/hysterical users about their accounts being deleted, even though they hadn't actually been, and a telling off from the boss.