Software Forestry 0x02: What We Talk About When We Talk About Tech Debt

Tell me if this sounds familiar: you start a new job, or roll onto a new project, or even have a job interview, and someone says in a slightly hushed tone, words to the effect of “Now, I don’t want to scare you, but we have a lot of tech debt.” Or maybe, “this system is all Legacy Code.” Usually followed by something like “but don’t worry! We’ve got a modernization effort!”

Everyone seems to be absolutely drowning in “tech debt”; hardly a day goes by where you don’t read another article about some system with some terrible problem that was caused by being out of date, deferred maintenance, “in debt.” We constantly joke about the fragile house-of-cards nature of basically, everything. Everyone is hacking their way, pun absolutely intended, through overgrown forests.

There’s a lot to unpack from all that. Other engineering disciplines don’t beg to rebuild their bridges or chemical plants after a couple of years, but they also don’t need to; they build them to last. How does this happen? Why is it like this?

For starters, I think this is one of those places where our metaphors are leading us wrong.

I can’t now remember when I first heard the term Technical Debt. I think it was early twenty-teens, the place I was working in the mid-aughts had a lot of tech debt but I don’t ever remember anyone using that term, the place I was working in the early teens also had a lot, and we definitely called it that.

One of the things metaphors are for is to make it easier to talk to people with a different background—software developers and business folks, for example. We might use different jargon in our respective areas of expertise, but if we can find an area of shared understanding, we can use that to talk about the same thing. “Debt” seems like a kind of obvious middle-ground: basically everyone who participates in the modern economy has a basic, gut-level understanding of how debt works.

Except, do they have the same understanding?

Personally, I think “debt” is a terrible metaphor, bordering on catastrophic. Here’s why: it has very, very different moral dimensions depending on whose talking about it.

To the math and engineering types who popularized the term, “debt” is obviously bad, bordering on immoral. They’re the kind of people who played enough D&D as kids to understand how probability works, probably don’t gamble, probably pay off their credit cards in full every month. Obviously we don’t want to run up debt! We need to pay that back down! Can’t let it build up! Queue that scene in Ghostbusters where Egon is talking about the interest on Ray’s two mortgages.

Meanwhile, when the business-background folks making the decisions about where to put their investments hear that they can rack up “debt” to get features faster, but can pay it off in their own time with no measurable penalty or interest, they make the obvious-to-them choice to rack up a hell of a lot of it. They debt-financed the company with real money, why not the software with metaphorical currency? “We can do it, but that’ll add tech debt” means something completely different to the technical and business staff.

Even worse, “debt” as a metaphor implies that it ends. In real life, you can actually pay the debt off; pay off the house, end the car payment, pay back the municipal bonds, keep your credit cards up to date, whatever. But keeping your systems “debt free” is a process, a way of working, not really something you can save up and pay off.

I’m not sure any single metaphor has done more damage to our industry’s ability to understand itself than “tech debt.”

Of course, the definiton “tech debt” expanded and has come to encompass everything about a software system that makes it hard to work on or the developers don’t like. “Cruft” is the word Fowler uses. “Tech debt”, “legacy”, “lack of maintenance” all kind of swirl into a big mish-mash, meaning, roughly, “old code that’s hard to work on.” Which makes it even less useful as a metaphor, because it covers a lot of different kinds of challenges, each of which calls for different techniques to treat and prevent. In fairness, Fowler takes a swing at categorizing tech debts via the Technical Debt Quadrant, which isn’t terrible, but is a little too abstract to reflect the lived reality.

This is a place where our Forestry metaphor offers up an obvious alternate metaphor: Overgrowth. Which gets close to heart of what the problem feels like: that we built a perfectly fine system, and now, after no action on our part, its not fine. Weeds. There’s that sense that it gets worse when you’re not looking,

There’s something very vexing about this. As Joel said: As if source code rusted. But somehow, that system that was just fine not that long ago is old and hard to work on now. We talk about maintenance, but the kind of maintenance a computer system needs is very different from a giant engine that needs to get oiled or it’ll break down.

I think a big part of the reason why it seems so endemic nowadays is that there was a whole lot of appetite to rewrite “everything for the web” in either Java or .Net around the turn of the century, at the same time a lot of other software got rebuilt mostly from scratch to support, depending on your field, Linux, Mac OS X, or post-NT Windows. There hasn’t been a similar “replant the forest” mood since, so by the teens everyone had a decade-old system with no external impetus to rebuild it. For a lot of fields, this was the first point where we had to think in terms of long term maintenance instead of the OS vendor forcing a rebuild. (We all became mainframe programmers, metaphorically speaking.) And so, even though the Fowler article dates to ’03, and the term is older than that, “Tech Debt” became a twenty-teens concern. Construction stopped being the main concern, replaced with care and feeding.

Software Forests need a different kind of tending than the old rewrite-updates-rewrite again loop. As Foresters, we know the codebases we work on were here before us, and will continue on after us. The occasional greenfield side project, the occasional big new feature, but mostly out job is to keep the forest healthy and hand it along to the next Forester. It takes a different, longer term, continuous world view than counting down the number of car payments left.

Of course, there’s more than one way a forest can get out of hand. Next Time: Types of Overgrowth, catalogued