It is not uncommon that an existing piece of non-trivial software gets re-written from scratch. Personally, I find this preference for a greenfield approach interesting, because it is not something I share. In fact, I believe that it is a fundamentally flawed approach in many cases, so why are people still doing this today?
Probably because they just like it more and also it is perceived, at least when things get started, as more glorious. But when you dig deeper the picture changes dramatically. Disclaimer: Of course there are situations when re-starting is the only option. But it typically involves aspects like required special hardware not being available any more.
When I started writing this post with making some notes, it all started with technical arguments. They are of course relevant, but the business side is much more critical. Just re-phrase the initial statement about re-writing to something like
Instead of gradually improving the existing software and learn along the way, we spend an enormous amount of money on something that delivers no additional value compared to what we have now. For this period, which we currently estimate to be 2 years (it is very likely to be longer), apart from very minor additions, the business will not get anything new, even if the market requires it; so long-term we risk the existence of the organization. And yes, we may actually loose some key members of staff along the way. Also, it is not certain that the new software ever works as expected. But should it really do, the market has changed so much, that the software is not very useful for doing business anyway and we can start all over again.
Is there anyone who still thinks that re-writing is generally a good idea?
Let us now change perspective and look at it from a software vendor’s point of view. Because the scenario above was written with an in-house application in mind. What is different, when we look at a company that develops and sells enterprise software? For this text the main properties of enterprise software are that it is used in large organizations to support critical business processes. How keen will customers be to bet their own future on something new, i.e. not tested? But even if they waited long enough for things to stabilize, there would be the migration effort. And if that effort comes towards them anyway, they may just as well look at the market for alternatives. So you would actively encourage your customer base to turn to the competition. Brilliant idea, right?
What becomes clear looking at things like that, is what the core value proposition of enterprise software is: investment protection. That is why we will, for the foreseeable future, continue to have mainframes with decades-old software running on them. Yes, these machines are expensive. But the alternatives are more expensive and in addition pose enormous risk.
In the context of commercial software vendors one argument for a re-write is that of additional revenue. It is often seen as easier to get a given amount of money for a new product than an improved version of something already out there. But that is the one-off view. What you typically want as a software vendor is a happy customer that pays maintenance every year and, whenever they need something new, first turns to you rather than the competition for options. Also, such a happy customer is by far the best marketing you can get. It may not look as sexy as getting new customers all the time, but it certainly drives the financial bottom line.
Switching over to the technical side, there are a few arguments that are typically made in favor of a restart. My favorite is the better architecture of the new solution, which will be the basis for future flexibility, growth, etc. I believe that most people are sincere here and think they can come up with something better. But the truth is that unless someone has done something similar successfully in the past, there is a big chance that the effort is hugely underestimated. Yes, technology has advanced and we have better languages and frameworks. But on the other hand the requirements have also grown dramatically. Think about high availability, scalability, performance and all the others. Even more important, though, is the business side. With something brand new people will have greatly increased expectations. So giving them something like-for-like will probably not be seen as success.
The not-invented-here syndrome is also relevant in this context and particularly with more junior teams. I have seen a case when an established framework used in more than 9,000 business-critical (i.e. direct impact on revenue) installations was dismissed in favor of something the team wanted to develop themselves. And I can tell you that the latter was a really bad implementation. Whether it was a misguided sense of pride or a fundamental lack of knowledge I cannot say. But while certainly being the most extreme incarnation I have seen so far, it was certainly not the only one.
So far my thoughts on the subject. Please let me know what you think about this topic.