There is one thing that will have the hair on the back of my neck stand up. A sentence, that I hear in my worst nightmares, just before I wake bathed in sweat. Fifty-fifty, I shit myself if I hear that sentence. And that's when I am awake...

The sentence is: "Oh, don't worry, we just have like two of them."

Implying, we have a dataset and two of them behave differently. How different, I ask. Oh, one line explanation, then the dreaded sentence. Meaning, we don't want to go too deep into the exceptions, because that special rule is nonsensical, not written down, cannot really be justified to auditors if they happen, and I bill them for the time, they want to move on to other things.

I painstakingly explain that I need to know all the special cases. Because they will either crash the system or, worse, the results will be unreliable. They grudgingly explain it. 5 minutes later, they next table, and again, the same data also causes an exception here. I hear it again. "It's only one or two items from all our thousands of customers..." And I get the feeling that these 1 or 2 items get complete special treatment throughout the whole system. And no one knows the complete extend or protocol of it. And it repeats...

Another time, and then another... and then it stops... And the dread rises. The customer realized I make a problem out of the special treatment of this one thing. He stops pointing out the special treatment. Suddenly, process over process without exceptions... Before, we always did something different everywhere...

And finally I awake, bathed in sweat and realize, I am still in the conference room. I passed out... Alright, too dramatic... I quietly resigned to have the complain afterwards and destroy the clean architecture by dribbled in corrections and exceptions.