It doesn’t happen often, until you make e.g. a ticketing system with a pool of ticket handlers that claim a ticket to work on it, instead of a sole ticket handling responsible, and now it happens dozens of times a day and the customer is irate at such incompetent software.

I may at an earlier part of my career, when I knew far less about building robust software, have stumbled into such an experience.

"We dont need to worry about that because it like a 1 in 100000 chance of occurring"

Proceeds to do millions of transactions a day.