Friday, 29 October 2010

Against technical debt

Technical debt is a very useful concept for explaining the consequences of dirty code to management. However, there is a problem that I have with the debt metaphor. The phrase technical debt implies that it's possible to avoid the debt. If I don't write shoddy code today, I wont have to pay for it tomorrow.

This obscures the fact that though dirty code costs more than clean code, every line of code impedes your agility. Sometimes product owners ask for features that compromise a system's architecture or domain model. When I've tried to describe the technical debt that will be incurred by an awkward feature, I've (quite reasonably) been asked how much effort it would take to "do it properly". I'm stumped, because no matter how thoroughly I implement the feature, it will still cause problems down the line.

Sometimes I fall back on depreciation, which I can use to explain anything that reduces the system's ability to meet future needs. Unlike debt, depreciation isn't automatically reversible. I've also considered that fear-driven estimation might produce estimates that more accurately reflect the long-term cost of a story.

I don't want to see the technical debt analogy deprecated, but I do want to encourage people to think critically about how they use it, because all metaphors have their limits.

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