Technical debt

Technical debt is the future cost of choosing the quick solution over the right one. The metaphor is exact: you borrow speed today and repay it as interest on every subsequent change, because each one has to work around the shortcut you took.

The part people miss is that debt is a legitimate instrument. Taking it on deliberately to test something before it is worth building properly is good judgement; the failure is taking it on accidentally and never writing it down. Undocumented debt does not stop compounding, it just stops being visible, and it presents itself two years later as "everything here takes longer than it should" with no traceable cause.

The practical test is not whether the code is ugly but whether it slows the next change. Ugly code in a part of the system nobody touches costs nothing. Clean-looking code in a hot path with three special cases can cost a week a month.

Worked: a hard-coded workaround saves three days at launch. Eleven months later it has been worked around four times, at roughly two days each, and the fix that would once have taken three days now takes eight because four things depend on the shortcut. The three days borrowed cost sixteen.