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Technical Debt — Defined

Designing software that is meant to be used requires that you put the user experience front-and-center when coming up with the design.

However, when  you have functionality that you need to add to your system you have two ways to do it,

  1. Quick and messy – you are sure that it will make further changes harder in the future. This involves actions like hardcoding parameters or bringing in libraries that you don’t completely understand.
  2. The other results in a cleaner design, but will take longer to put in place.

Ward Cunningham coined a wonderful metaphor (Technical Debt) to help us think about this problem.

In this metaphor, doing things the quick and dirty way sets us up with a technical debt, which is similar to a financial debt. Like a financial debt, the technical debt incurs interest payments, which come in the form of the extra effort that we have to do in future development because of the quick and dirty design choice. We can choose to continue paying the interest, or we can pay down the principal by refactoring the quick and dirty design into the better design. Although it costs to pay down the principal, we gain by reduced interest payments in the future.

The metaphor also explains why it may be sensible to do the quick and dirty approach. Just as a business incurs some debt to take advantage of a market opportunity developers may incur technical debt to hit an important deadline. The all too common problem is that development organizations let their debt get out of control and spend most of their future development effort paying crippling interest payments.

I’ve made some choices during my career where hard deadlines, or the limited maintenance nature of the project meant that the effort for very clean code and architecture was not justified. However, one practice that I would advocate is to keep a copy of Bugzilla around where you can log all the ‘todos’ required to refactor, clean-up and enhance robustness in your project.

When you have debt, you have to keep track of it so that you can pay it off. Any other alternative is reckless and irresponsible. The metaphor hold equally well in the domain of software engineering as it does in the field of personal (or corporate) finance.

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