The cost of a piece of debt is its messiness multiplied by how often you go near it. A horrible module that hasn’t changed since 2023 costs almost nothing today. You’re not reading it or extending it. Refactoring it is paying down a loan that isn’t accruing interest. Meanwhile the mediocre little helper that 40 features lean on, the one edited every other week, is quietly the most expensive code you own. It’s usually not on anyone’s list because it doesn’t look scary.

I had not thought about tech debt in this way before. It makes perfect sense to focus on paying off the tech debt where you spend the majority of your time working, and hence accruing interest on.