Fix vs Replace

I was thinking about when to fix a piece of software versus replace it as part of our normal software lifecycle, prompted by a discussion at work of a particular piece of software. The software in question works great, but nobody is confident that they are successful when changes do need to be made. Part of the lack of confidence is because changes are only made once or twice a year, so getting it set up and running locally and testing it is a chore, plus it turns into a complex process with many chances of failure. The other part is it runs on top of another library that nobody is really familiar with; the library isn’t used anywhere else in our stack, so nobody develops any familiarity with it. This particular piece of software is also critical to expanding our business, as it’s the primary way new client data is loaded into the system.

If we wanted to fix it, we could take the existing solid software and enhance it to make the setup and testing easier, or we could clean up the usage of the underlying library so it’s more intuitive. However, the decision was instead made to replace it with something totally new. I wasn’t involved in the decision, but became involved with the original piece of software after the fact to make a change while the replacement is still being developed. It seems like this software could be rehabilitated at first glance, but clearly someone else thought otherwise.

I know in general I’m biased towards fixing existing software. I’ve spent most of my career working on brownfield applications and building oddly shaped pegs to fit back into the oddly shaped holes of those applications. I think that I’ve done this because I enjoy it; building everything from scratch is almost too easy since there are so many fewer constraints involved. I get a different sort of satisfaction from it. I know I’m not the only one who has this particular tendency; the folks at Corgibytes are specializing in this sort of work. I’ve even been nostalgic for a codebase I’ve worked on – not the application but the codebase itself.

I feel like most organizations are biased towards replacing software because it lets you just say the entire thing is bad and try again instead of having to pick a particular thing to do or change. You don’t have to agree on what’s wrong with it, or get into details of what to change. This flexibility of scope leads to the quid pro quo rewrite where a piece of software is replaced with a new version that also contains a major new feature; this concept was introduced to me by Re-Engineering Legacy Software. Re-Engineering Legacy Software describes this as a bargaining tool to enable you to gain acceptance of a plan to do the rewrite, but I’ve always seen the business bring up the rewrite with the idea that they’re unhappy with the team’s ability to change a piece of software and this would clean up the underlying causes of the problems.

That’s the big problem: the current software has problems due to something. And unless you deal with whatever that “something” is, the new software probably is not going to be significantly better than the old. It may not have had the chance to become crufty yet, so it seems better when it’s new, but given a few years goes back to the same sorts of problems you had the last time. You need normal software processes that enable you to create and maintain quality software even as requirements change.

You need feedback into your initial processes of what caused the cruftiness to accumulate. This can be seen as a form of double-loop learning, where the feedback of what happened impacts how you see the world and thereby influences your decision-making process, not just the decisions themselves. If you are accumulating cruft because you put schedule pressure on the initial development resulting in a less modular design, the feedback to the decision-making process would be different than if you are accumulating cruft because the requirements changed radically. To make true long-term improvements, that’s the step you need to take, which sometimes might lead you to fix, and sometimes might lead you to replace.


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