Glossary
The deferred effort from earlier shortcuts in code or architecture. It does not disappear, it simply falls due later and at a higher price.
Ward Cunningham coined the term as a financial image: you borrow speed and pay interest. Debt taken on deliberately is a legitimate tool when a date matters. Debt taken on unknowingly is simply ignorance.
The interest does not arrive as an invoice, it shows up as lead time: what took two days three years ago now takes two weeks. That is exactly why it is noticed so late, because nobody sends a reminder.
How you notice it
Frequently asked
Not as a total but as lead time. Compare how long a typical change takes today against how long it would take in a healthy system. That difference times the number of changes per year is a number that triggers a decision.