AppleI had coffee with an acquaintance a while back who works in a software company. We were talking about their system and he referred to the “original sin”.

It immediately struck a nerve.

Whenever I (the “I” being a team, as it’s extremely rare to build anything by yourself) build a system, I make assumptions based on a number of factors. What I need to provide functionality immediately. Where I expect the system to go in the short term. Where I expect the system to go in the long term. What I need to do to make the system maintainable. What I need to do to make sure I can run the system.

All of these assumptions mix together into an architecture and a design. Similar to the way I imagine one would lay out a subdivision, the early choices (where to put roads and lots) effect later decisions (where trees, parks, and homes go, which homes get the best view).

Often, one or more of these assumptions is incorrect, and it is often one of the core decisions, rather than one of the ancillary ones. (Or, perhaps they both have an equal chance to be incorrect, but if it is a core assumption, I notice it more.) This is the “original sin”.

I can think back to all of the systems that I ran for any length of time in production (that is, with real customers) and name an original sin (at least one, oftentimes more).

What do you do with this mistake?

You can live with it

The mistake is embedded so deep, or the business is evolving so quick, or there are so many other features that it never makes sense to rectify the issue. It just sits in your system, bugging you when you see it, making new features more complicated to build.

You can rip it out

If you have the time and now know what you didn’t know when you first built the system, you can modify the system to remove the original sin. This can take time and effort, because it is embedded and probably touches many pieces of your system. It also may slow down or stop new development. When you are done, you’ll have a system that is better for the world your business is living in now. However, you may add a new original sin.

You can work around it

Instead of living with it (no change to it) or ripping it out (pulling it out at the roots), you can work around it. I’ve done this before by swapping out pieces of an original sin component. This is an iterative approach that that can be intermingled with feature development. This is the most pragmatic approach for long lived software.

You can abandon the system

If the system has a really fundamental original sin, and the technology world has moved on, you may consider abandoning the system, either for a new build or a new buy. Don’t think of the money you spent on the first system as wasted, think of it as tuition.

It is tough to make predictions about the future usage of your system. Building a system is a balance between getting it done and making it flexible enough to meet future needs. However, some decisions are so rooted in your system that they will have ramifications for as long as those systems are used. And some of the decisions you make will be wrong, and you’ll be confronted with that fact as long as you work on that system. It’s OK to make these mistakes, but when you see one, think long and hard about how best to rectify it, balancing development and business pain. Discuss it with your team, including non technical members, so that everyone understands the pain.

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