AT3 — Simplicity/Flexibility: The original technical debt tradeoff. Simple code is easier to write, easier to read, and faster to ship. Flexible code (with abstractions, indirection, proper layering) takes longer to build and requires more sophistication to understand. Debt is the choice to take simplicity now; the interest is the cost of acquiring flexibility later, when the system has grown and is harder to change.
AT7 — Automation/Control: Paying down debt through refactoring reduces manual control (the team must trust automated tests to verify that behaviour is preserved) but enables automation of future work (CI/CD, automated deployment). High-debt codebases resist automation because the code is too fragile for automated change; this perpetuates the manual processes that make debt expensive to address.