A couple of years ago I was working on a fairly large system with a complex (by necessity) access control architecture.

As is usually the case with those projects, it's awkward for developers to repro bugs that have to do with a user's accesses in production when we are not allowed to replicate production data in test, let alone locally.

We had a bug where I ended up making myself a new row in the production database for a thing I could have access to without affecting real data to repro it safely. I identified the bug so I could repro it in dev/test and removed the row and ensured everything worked normally, whew scary.

Have you ever walked into the office one day, and everyone is hunched over in a semicircle around one person's workstation, before one turns around to look at you and says - after a pause - "... ltlian?.."

Turns out I had basically "poisoned the well" with my dummy entity in a way where production now threw 500 for everyone BUT me who had transitive access to this post-non-entity. Due to the scope of the system, it had taken about a day for this to gradually propagate in terms of caching and eventual consistencies; new entities coming in was expected, but not that they disappear.

Luckily I had a decent track record for this to be a one-off. I sometimes think about how I would explain testing in prod and making it faceplant before going home for the day, other than "I assumed it would be fine". I would fire me.