A Taxonomy of Technical Debt

This is a fantastic article.<p>Contagion is a really great term. I&#x27;ve seen my poor abstractions be replicated by others on my team, to my horror -- &quot;don&#x27;t they see why I did that in this particular case, and not in this other case?&quot; Of course, that&#x27;s entirely, 100% my fault. I picked a poor abstraction, I put it in the code, I didn&#x27;t document it well enough, and of COURSE other programmers are going to look to it when solving similar problems. They should!<p>That said... Sometimes I spend a bunch of time finding the right abstraction for a feature that we end up not expanding. And then it feels bad that I spent all this extra time coming up with the &quot;right&quot; solution, instead of just hacking out something that works. Hmm...

This reminds me of the following, from the book Team Geek[1], chapter &quot;Offensive&quot; Versus &quot;Defensive&quot; Work:<p><i>[...] After this bad experience, Ben began to categorize all work as either “offensive” or “defensive.” Offensive work is typically effort toward new user-visible features—shiny things that are easy to show outsiders and get them excited about, or things that noticeably advance the sexiness of a product (e.g., improved UI, speed, or interoperability). Defensive work is effort aimed at the long-term health of a product (e.g., code refactoring, feature rewrites, schema changes, data migra- tion, or improved emergency monitoring). Defensive activities make the product more maintainable, stable, and reliable. And yet, despite the fact that they’re absolutely critical, you get no political credit for doing them. If you spend all your time on them, people perceive your product as holding still. And to make wordplay on an old maxim: “Perception is nine-tenths of the law.”</i><p><i>We now have a handy rule we live by: a team should never spend more than one-third to one-half of its time and energy on defensive work, no matter how much technical debt there is. Any more time spent is a recipe for political suicide.</i><p>[1] <a href="http:&#x2F;&#x2F;shop.oreilly.com&#x2F;product&#x2F;0636920018025.do" rel="nofollow">http:&#x2F;&#x2F;shop.oreilly.com&#x2F;product&#x2F;0636920018025.do</a>

It&#x27;s a great article, but I do have one quibble.<p>&gt; A hilariously stupid piece of real world foundational debt is the measurement system referred to as United States Customary Units. Having grown up in the US, my brain is filled with useless conversions, like that 5,280 feet are in a mile, and 2 pints are in a quart, while 4 quarts are in a gallon. The US government has considered switching to metric multiple times, but we remain one of seven countries that haven’t adopted Système International as the official measurement system. This debt is baked into road signs, recipes, elementary schools, and human minds.<p>A not-so-hilariously stupid mistake is to think that the traditional measurement system is stupid. His picture illustrates one of its virtues: the entire liquid-measurement system is based on doubling &amp; halving, which are easy to perform with liquids. The French Revolutionary system, OTOH, requires multiplying &amp; dividing by 10, which is easy to do on paper or with graduated containers, but extremely difficult to do with concrete quantities (proof: with one full litre container and two empty containers, none graduates, attempt to divide the litre into decilitres).<p>The <i>real</i> foundational debt is that we use a base-10 system for counting, due to the number of fingers &amp; thumbs on our hands, rather than something better-suited to the task. If we fixed <i>that</i> problem, then suddenly all sorts of numeric troubles would vanish. There&#x27;s actually a lot to be said about the Babylonian base-60 system, to be honest.

Great article, loved how the examples were presented.<p>In my time as an engineer, I&#x27;ve found that thinking of tech debt as financial debt also helps. There is the initial convenience (borrowed money) of using the debt-ed approach. Then there is fix cost as Bill Clark name it, i.e. how much to pay back the debt if it were money. The impact is akin to the amortization schedule, i.e. what is the cost every time. For normal money, amortization schedule is over time, but for tech debt it is over usage. The amortization schedule of tech debt is discounted over time, as with money, _now_ is more important that _later_.<p>Contagion is a great concept, and I think it is a better name than interest rate, as the debt will spread through the system, and not just linearly with time.<p>Tech debt is also multi-dimensional and not fungible like money, which makes it a harder thing to reason about.<p>But the good news is, in my opinion, that sometimes it is perfectly fine to default on some tech debt, and never pay it back, delete the code. Then taking that tech debt was a win, if the convenience was more than the amortized payments.

In data warehousing and BI, it&#x27;s MacGyver and data technical debt all the way down. MacGyver because of all the &quot;urgent&quot; reports whipped up for CEO, duplicate copies of data and the reports done by consultants who barely understand industry. Data dept because of all the bugs and changes passed down as data from source system.

What about &quot;fear&quot;?<p>The most pernicious thing about technical debt, in my opinion, is that it creates fear in the sense of &quot;I don&#x27;t want to touch that module&quot;.<p>Even if you try to be objective and use hard facts to overcome the fear, it doesn&#x27;t matter, because fear destroys creativity, so you&#x27;ve already lost.

I might have missed it, but missing from the taxonomy: &quot;Pay In Full&quot; Debt.<p>In this debt, you pay the entire cost until the last use of it is cleaned up.<p>This kind of debt is especially insidious because there is no incremental benefit to cleaning it up.

Reminds me of risk analysis: Impact times Probability equals Risk.<p>Contagion seems like a probability factor. Impact is the cost of leaving things unchanged. Fix cost is the cost of fixing the problem.<p>Risk management in this context then means comparing Impact cost to Fix cost in terms of impact for the business.

Somewhat aside, but the brain having to &quot;flip&quot; visual information because it&#x27;s &quot;upside down&quot; seems suspect to me. Turn it sideways while maintaining all the connections it has to the rest of the body, and what changes? Is it getting visual information sideways that it has to rotate now? Probably not.

There are writers who just ooze technical depth of understanding - i thinks it&#x27;s something to do with trying to explain something at a laypersons level, but leaving many assumptions just there for the reader to follow. It&#x27;s almost the opposite of baffling with bullshit.<p>Good read and a really useful concept

I am a senior product manager for a large financial technology company.<p>Over the years I have learnt to become comfortable with allowing my engineering teams to refactor code whilst delivering new functionality.<p>This has been a process and largely one of trust between me and the engineering leads.<p>It has also helped that I have seen payback from the investment made from reducing down the debt in terms of us delivering new functionality quicker and less error prone code. Although, this payback can take a while to see (6months + which is a long time for a product person operating in a competitive space!)<p>Most of my managers don&#x27;t get this or if they do they are too blinded by immediate kpi&#x27;s from further above they can&#x27;t justify it so in most cases I just tell the engineering guys to add a spread to their estimates to cover the paydown of the debt.<p>Over they years this has definitely helped me build tighter relationships with engineers which as any product manager knows can have huge benefits.

I find it&#x27;s always worth asking &quot;will this get better over time, or worse&quot; for everything, ever. Folks just fail to see past the next few months, having at least one person in the room asking this question makes them at least ignore it intentionally instead of complacency.

&quot;I’ve rarely encountered discussions of contagion.&quot;<p>This surprised me: contagion is a good metaphor because it is a compounding measure of the growth of the problem. Just like an interest rate (a compounding measure of the growth of debt).<p>Most senior developers I&#x27;ve met have considered the interest rate of the debt, which seems like it has been renamed here as contagion. Maybe I&#x27;ve been lucky to just know smart people!<p>From the point of view of explaining these concepts, I&#x27;d suggest keeping the metaphors consistent. Tech debt should have an amount owed and an interest rate, tech infection (?) should have a potency and a contagion level.

At pretty much every game studio there is an epic internal battle of standard libs vs custom. std::string and [some custom string class] here it is AString is usually the spark. A constant of internal game development is that they think they can always build better strings, lists, dictionaries, collections etc than the standard lib, basically thinking the standard lib is as it was in the 90s and all the work that went into them is bunk. In some cases if you are really pushing memory and not writing custom allocators or using something like boost then yes, but in most cases the technical debt of custom classes written by an ancient from generations ago internally is more technical debt.<p>&gt; <i>One of the best examples of MacGyver debt in the LoL codebase is the use of C++’s std::string vs. our custom AString class. Both are ways to store, modify, and pass around strings of characters. In general, we’ve found that std::string leads to lots of “hidden” memory allocations and performance costs, and makes it easy to write code that does bad things. AString is specifically designed with thoughtful memory management in mind. Our strategy for replacing std::string with AString was to allow both to exist in the codebase and provide conversions between the two (via .c_str() and .Get() respectively). We gave AString a number of ease-of-use improvements that make it easier to work with and encouraged engineers to replace std::string at their leisure as they change code. Thus, we’re slowly phasing std::string out and the “duct tape” interface between the two systems slowly shrinks as we tidy up more of our code.</i><p>So now there are two string classes, that is technical debt... and one should be consolidated on and the arguments against std::string are sometimes valid but you can also do custom memory allocators or use better standard lib iterations.<p>EA even rewrote the whole standard lib EASTL [1] to adjust for some of these issues i.e. fragmented memory. Some games require it, some it is pure ego in game development teams. Game development teams have the highest ego driven development (EDD) I have ever seen and lots of <i>tricks</i> that take <i>five minutes</i> (but add 2-3 months to testing due to five minute solutions) but are more spaghetti than templates that write templates.<p>The one problem that comes about with your own standard lib or thinking you are better than boost or similar, is that the learning curve on the internal lib replacements add technical debt and start up costs, and the original guy that wrote them is long gone usually. Also, in the end portability suffers as there is invariably 3-4 versions of the internal libs.<p>Developers have to weigh the technical debt of your own custom classes outside standard libs and see if that outweighs the memory issues that may arise. Today most machines are not as affected by memory fragmentation issues and there is more cpu&#x2F;memory to go around, and where they are you can write custom allocators for std&#x2F;stl or use something like boost.<p>I do love Riot Games and all game development teams just I have never worked in one or with one that doesn&#x27;t have the standard lib vs custom battle and wastes lots of time when one isn&#x27;t standardized on or when not necessary. Some games and game engines require it, where they do you should fully commit one way or the other. Though going custom leads to slowdowns in coding for new devs and invariably there will be multiple versions of those internal libs over time that add up in the debt department.<p>[1] <a href="https:&#x2F;&#x2F;github.com&#x2F;electronicarts&#x2F;EASTL" rel="nofollow">https:&#x2F;&#x2F;github.com&#x2F;electronicarts&#x2F;EASTL</a>

In my experience often the term &#x27;technical debt&#x27; will be hijacked by product-oriented folks resulting in feature debt being presented as tech debt.

This seems far too focused on dev tech debt, which has a very narrow scope. I like the article, so I&#x27;m not knocking it, just offering a little perspective. As a senior sysadmin in the past my primary issues have been technical debt across the entire board, number one being too few hires for too much workload due to cheap or nearsighted execs, but I would definitely agree that contagion is a great term for how techdebt grows faster the longer it&#x27;s left alone.<p>It&#x27;s worth remembering the CTO and senior sysadmin and a few others are dealing with all the tech debt of the entire company and IT department of which dev is only a subset (of course this depends on the company, but on HN sometimes I see convos like this where it feels devs are just talking at each other and not receiving much outside feedback.)

I&#x27;ve been binge listening to Software Engineering Radio for the past few months. I am currently listening to an episode where they are talking about technical debt.<p>He has the opinion that clean code is not as important as shipping code - ship the code first and then refactor as needed after you get customers.<p><a href="http:&#x2F;&#x2F;www.se-radio.net&#x2F;2015&#x2F;04&#x2F;episode-224-sven-johann-and-eberhard-wolff-on-technical-debt&#x2F;" rel="nofollow">http:&#x2F;&#x2F;www.se-radio.net&#x2F;2015&#x2F;04&#x2F;episode-224-sven-johann-and-...</a>

“We gave AString a number of ease-of-use improvements that make it easier to work with and encouraged engineers to replace std::string”<p>Are you absolutely sure this itself won’t become Foundational technical debt? You seem overly confident, given the metrics, that replacing std::string is a good decision.

I love this article. Quickly breaks down the types of debt.

(MacGyver&#x27;s name is Angus!?)

I would love the idea of a technical credit score. For example, if you’re the kind of dev that racks up technical debt and never pays it down, you should have a shitty technical credit score, and be considered a poor hire. Whereas someone with great credit, would be a great asset to bring onto the team.

Cool write up and classification system. A category that affects us is VendorDebt. Things that are inflicted on us by external vendors. Classifying then in a similar manner might help us decide which vendors to dump.