Technical debt
On this page 9 topics
Overview
Topics
- Classification
- prioritization
- incremental remediation
Learn first
3.5 h of practice (estimate)
Learning outcomes
- Classify debt (deliberate/inadvertent, prudent/reckless) and describe its interest in concrete costs.
- Build a debt register and prioritize by cost of delay and risk.
- Pay debt down incrementally alongside feature work (boy-scout rule, strangler techniques).
- Make the business case for a debt investment.
Lessons
Lab and exercises
Lab
SRC-017-LAB1 · Shop debt register
Outcomes: 1–4 · Time: ~3.5 h Build a debt register for Shop Platform with classified items, cost estimates, and a one-quarter paydown plan using incremental techniques. Pitch it to role-played product leadership. Acceptance: at least one item approved on its business case.
Exercises (assessment: pitch and register review)
| ID | Outcome | Task |
|---|---|---|
| SRC-017-EX01 | 1 | Classify five examples into the deliberate/inadvertent and prudent/reckless quadrants and say which are not debt at all. |
| SRC-017-EX02 | 1 | Estimate the interest on a module touched 12 times a quarter with 1.5 extra days per change and one incident. State ranges. |
| SRC-017-EX03 | 2 | Build a five-item register with costs and rank them by payback and risk. |
| SRC-017-EX04 | 3 | Write an incremental plan to remove a God class OrderService over a quarter without a rewrite. |
| SRC-017-EX05 | 4 | Write the one-page business case for adding tests and extracting pricing, with options and measures. |
| SRC-017-EX06 | 2 | Case: debt in a module nobody will change for a year. Decide priority and justify. |
Show solutions
- EX01 Examples should show that a known shortcut with a repayment plan is prudent; a missing feature or a bug is not debt; skipped tests with no plan is reckless.
- EX02 12 × 1.5 = 18 engineer-days per quarter, with a range such as 14 to 22, plus the incident cost.
- EX03 Rank by payback (fix cost divided by monthly interest) and adjust for risk items such as security that rank first regardless.
- EX04 Add characterization tests, extract responsibilities one at a time behind interfaces, route new features to the new classes, delete old code as it empties, release each slice.
- EX05 Problem, evidence, cost of delay, options (do nothing, partial, full), cost, expected outcome and metrics, checkpoint.
- EX06 Low priority: little interest is paid; revisit if work in that area is planned.
- Outcome 3 is also covered by the lab plan and Q06-Q07.
Workplace evidence: a debt item you got prioritized and delivered.
Quiz
Outcomes: O1 classifying debt and its interest · O2 register and prioritization · O3 incremental paydown · O4 business case.
A self-check for you: nothing is graded, saved or sent anywhere. Choose an answer, then check it. You can try again as often as you like.
Practical part
Pitch and register review (SRC-017 assessment), plus the SRC-017-LAB1 register and pitch. Pass: at least 8/10 on the quiz, a register with costs for every item, and at least one item approved on its business case.
Common mistakes
"rewrite" as the remediation; debt lists with no costs.
Assessment
Pitch and register review.
Workplace evidence
A debt item you got prioritized and delivered.
Career relevance
Technical strategy (SRA-010) and modernization (ARC-010).