Steve McConnell has pretty nice video presentation on Managing Technical Debt that casts the whole issue in business value terms. I like that approach since we always need some credible (to the business) justification for spending Other People's Money (OPM)
McConnell, of course, has a lot of bona fides to speak on this topic, having been a past editor of IEEE Software and having written a number of fine books, like "Code Complete".
In McConnell's view, technical debt arises for three reasons:
- Poor practice during development, usually unwitting
- Intentional shortcuts (take a risk now, pay me later)
- Strategic deferrals, to be addressed later
- Risk adjusted cost of debt (expected value),
- Opportunity cost of debt, cost of debt service -- which Steve calls debt service cost ratio (DSCR), a term taken from financial debt management -- and
- The present value of cost of debt.
One point well made is that technical debt often comes with an "interest payment". In other words, if the debt is not attended to, and the object goes into production, then there is the possibility that some effort will be constantly needed to address issues that arise -- the bug that keeps on bugging, as it were.
Interest payments factored in
To figure out the business value of "pay me now, pay be later", the so-called interest payments need to be factored in.
In this regard, a point well taken is that debt service may crowd out other initiatives, soaking up resources that could be more productively directed elsewhere. Thus, opportunity cost and debt service are related.
Bottom line: carrying debt forward is not free, so even strategic deferrals come with a cost.
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