Mon
12
Nov 2018

There is this term "technical debt" used in the world of software development as a metaphor to describe poor quality of source code (or the lack of documentation, tests etc.), whether it's a bad overall architecture, quick and dirty hacks in some places, or any kinds of software anti-patterns. It makes the code harder, slower, and less pleasant to maintain, fix, and expand. It's called "debt" because, just as the financial debt, it causes some "interest" that needs to be paid, in form of increased maintenance cost and more bugs to fix, until it's repaid (refactoring or rewrite of bad code, completing work that was missing and left "TODO"). It is most frequently caused by lack of time due to deadlines imposed by business people - lack of time to fully understand the requirements and design good solution, to read and understand the existing codebase, to refactor or rewrite if the code is already bad.

Some people say that "technical debt" is a bad metaphor. There was this one article I can't find now which argued that bad code is unlike real-world debt because we don't need to pay "interest" until we actually need to go back to and modify the specific piece of code where we made a dirty hack. I don't agree with it. Sure things in software development are harder to measure and estimate quantitatively than in the business world, but I think that "technical debt" is a good metaphor. Just like in real life, there are different kinds of debt. It depends on who do you borrow money from:

- Leaving bad code in a place where you and everyone else in the team may never need to look again is like borrowing money from you family or best friend. You know the debt is there, but you may postpone paying it off indefinitely and you will still be fine.

- Leaving bad code in a place where you periodically need to make fixes and other changes is like borrowing money from a bank. You have to periodically pay interest until you repay it all.

- Finally, making ugly hack in a critical piece of code that you touch constantly is like being in so desperate need for money to borrow from mafia. You better repay it quickly or you will get in trouble.

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