The title is as ambiguous as it is because I guess it applies to all kinds of work.

The only software of consequence I've ever written is interfacing with specialized measurement equipment in a production environment. It controls the devices, reads and evaluates the results, does some basic and some more advanced statistics, saves everything into CSV files and gives a one page text only printout.

In the 25 years I developed and maintained that ol' piece of junk, several tens of millions of components were evaluated by it. Yeah, I know exactly what you mean. :)

When you dive into an old avenue in your code and you hope you left enough documentation so you'll only have to compile and test two or three times.

When you find something really dumb and overengineered but are afraid to change it because it might break something else,

When you have to implement measures to make sure your users don't take short cuts because each measure takes a minimum of 450 ms plus some time to manually reposition the adapter plus couple 10s of milliseconds of contact settling time. Wait for the acoustic feedback from the computer, before you disconnect the DUT. Or else it get's the hose again :)

I just tore an entire webapp apart because a foundational function wasn't intuitive enough