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Technical Debt

posted under category: Software Quality on May 25, 2010 by Nathan

Technical Debt has been talked about a lot, but I have been thinking about pretty hard lately. Here's the concept: Make economic analogies for application development to help you (and especially your boss) understand code quality.

Let me lay it down so you can pick it up.

When you write code, you're making a monetary investment, be it in your own time or knowledge, there's been money spent. If it's not literal money, suspend your disbelief for a second when we pretend that your work is worth some arbitrary amount of cash. There's an amount you should spend to complete a given application, especially to do it right.

Now, when you take a shortcut in your programming, you save money up front. You can finish faster, but you're borrowing time, thus borrowing money. Eventually, that money has to be paid back, and you will pay it back.

Paying back technical debt means refactoring the application to undo those coding shortcuts, adding unit tests, making the application maintainable and adhering to best practices. The closer you are to the time you acquired the debt, the easier it is to pay it off. Think of credit cards; pay those off at the end of the month or else you accumulate interest.

Oh, and it's the interest payments that will really kill you.

Until you pay off that technical debt, every time you touch the application, you have to pay interest. In the past, you borrowed time from the future. Now the cruft in the code makes any subsequent task take longer. That is your interest payment. It comes off the top and you never pay it off until you remove the crufty code.

Code with high technical debt tends to be brittle. One change means everything breaks, so we spend our time being extra careful, or by accidentally creating a wide range of errors across the application. Interest makes programming harder, and harder is not what we need.

Nathan is a software developer at The Boeing Company in Charleston, SC. He is essentially a big programming nerd. Really, you could say that makes him a nerd among nerds. Aside from making software for the web, he plays with tech toys and likes to think about programming's big picture while speaking at conferences and generally impressing people with massive nerdiness and straight-faced sarcastic humor. Nathan got his programming start writing batch files in DOS. It should go without saying, but these thought and opinions have nothing to do with Boeing in any way.
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