Code reuse considered harmful

The title is intended to call for attention. This post is about one perspective of software development in the light of my own experience in the area, it won’t contain anything really revealing and is not to be taken as an absolute true for life. It’s a rant. I hope you have a good time reading it, feel free to leave me any kind of feedback.

I see a bunch of people praising reuse as being the prime thing of good software development, and few talking about replaceability. There seems to be a constant seek to avoid writing code that is used only once, as if it was a really bad thing. Then we end up with software that is made of conceptual factories that create factories that create the things the software really needs, yes there are two levels of factories, or more. Is this really necessary? How much time do we save by this extreme look for reusing code?

First, let me ask and answer a simple question: why duplicated code is annoying? Well, duplicated code makes it harder to change stuff. When you have the same piece of code written multiple times in a code base and you find that it needs a change, e.g. bug fix or new feature, you will need to change it in all places. Things can get worst if you don’t know all places where the code is duplicated, so you may forget to change one of these spots. The result is that duplicated code is a sign of harder maintenance and a fertile ground for further bugs to spawn. That’s why we learned to hate it. We started fighting this anti-pattern with all strength we had.

Code reuse is the perfect counter to code duplication, right? Sure, it is right, if we reuse a piece of code in two places, we have no duplication between these places. So, we did it! We found the Holy Grail of code quality, no more duplicated code, yay! But something unintended happened. Remember the old saying: with great powers, comes great responsibility. People started to be obsessed with it. As soon as they learned to use the hammer of code reuse, everything turned into a nail, when it didn’t work out in the first hit, they adjust the size of the hammer and hit it again with more effort.

This seek after code reuse led us to a plethora of abstractions that seems to handle every problem by reusing some code. Don’t get me wrong, lots of them are useful, these are the ones that were created from observation. The problem is the ones that are created from “it’s cool to abstract”, or other random reason that is not true observation. We see frameworks after frameworks that try to fit every problem of the world into a single model. Developers learn to use these frameworks and suddenly find out that the framework creator is wrong and create yet another abstraction over it or creates yet another framework that tries to use a different model to solve the world.

What happens when we have a bug in one of these abstractions or we need to enhance it? Silence, for a while, then the sky turns black, you take a break, go for a walk, come back to your computer and start blaming the other developer that created the bug or that “got the abstraction wrong”, because your vision was the right one. What happened? We reused code to avoid code duplication, but we are still having the same problems: code that is hard to maintain and evolve.

My guess? We missed the enemy. Code duplication is not our enemy. Maintenance problem and rigidity of code is.

My tip? Give more focus on replaceability of code instead of reuse in your talks, codes, classes, etc. Create the right abstraction to fix the problem at hand in a way that is easy to replace the underlying code when needed. Some time in the future, you will need to change it anyway. That’s what agile methodologies try to teach us: embrace change. Planning for a design to be reused says: “my design will be so awesome, that I will reuse it everywhere.” That’s what agile says: “your design will need to change sometime, because the requirements will change, plan for the replaceability of it.” People are doing things like service oriented architecture in the wrong way because they are looking for reuse of services and not for replaceability of services, they end up with a Big Web of Mud.

That’s all folks. Thanks for your time.

Premature optimization: it’s not just about code

When we talk about performance, we shouldn’t look only to performance of code execution. There are more types that we should care about, like time to market, development time and processes. Actually, we shouldn’t look into any of the performance measures at a single perspective. As I see, all these measures sums up to constitute a single value of business performance.

There are lots of things that can slow down your business, and if you have a slow business, you’ll have a hard time to keep pace with your rivals. As you discover that some areas of your company may be slowing you down, you may become tempted to add key performance indicators to each step trying to squeeze all possible value out of each part of your processes. This can bring up a whole new set of problems, your business can be seen as a complex system and it will adapt itself to render good results even in chaotic scenarios. [1]

So, to avoid going nuts with indicators all over the place, you decide to avoid bottlenecks from the start. To each and every new thing you need to deliver, you’ll start a precise planning routine, choosing among a plethora of providers, technologies and unicorns to avoid at all costs to have a new bottleneck in the future. This is what I like to call premature optimization in business performance.

Simply put: you can’t have a business if you don’t have a business. How can you possibly know all the events that will happen to have an impact in the decision you take today? You can’t.I’m not saying that planning is wrong or a Bad Thing™. What I really want to avoid is losing energy on stuff that won’t make a difference. You may spend a whole year choosing between apples and oranges, and in the end be crushed by some weirdo playing around with random technology. Why? Because he was not worried about future bottlenecks. He was really trying to do something cool, and he did it while you were arguing in endless and purposeless meetings.

You’re always trading performance measurements. For example, everyone is talking about service oriented architecture (SOA), but what does it really means in terms of business? It means a tradeoff between code execution performance and others benefits to the business as a whole, like decentralized grow and continuous delivery. Or, you may look at the difference between Apple’s App Store and Google’s Play Store model. There is a huge tradeoff of quality assurance and time to market between these two players: one offers their customers (smartphone owners), quality assured apps; the other offers their customers (operating system users), fast time to market for their apps.

The big question really is: what are you trying to deliver to your customer? Are you trying to deliver software over time or value over time? I bet most of you are trying to deliver value over time, so why bother with premature optimization of technologies or processes? Let the bad stuff to die on its own: failing fast is orders of magnitude better than not doing anything at all. And let the good stuff to accompany you to where you want to go.

Don’t bother guessing the future, embrace the uncertainty of life: you can’t predict how a complex system will behave, you can’t know how your systems, services or whatever you are doing will be used in the real world. Put it into the wild, take the complaints and tune it (or throw it away) afterwards, this is a constant process. [2]

Start measuring how much you are delivering over time and stop over-planning. Your end goal is to deliver stuff. The world couldn’t care less about what you can do, it only cares about what you do.


  1. Complex Systems and Key Performance Indicators – M├írcio Geovani Jasinski
  2. Complaint-Driven Development – Jeff Atwood