A contract that needs to be maintained at some level of quality even when you're deploying or overloaded.

Load shedding is a pretty advanced topic and it's the one I can think of off the top of my head when considering how Chesterton's Fence can sneak into these designs and paint you into a corner that some people in the argument know is coming and the rest don't believe will ever arrive.

But it's not alone in that regard. The biggest one for me is we discover how we want to write the system as we are writing it. And now we discover we have 45 independent services that are doing it the old way and we have to fix every single one of them to get what we want.