[pm90]

I imagine it depends on the situation.

Complete re-writes can sometimes help you elliminate a lot of technical debt and move faster if you do it right the second time. You can use different architectures, better tooling etc. So sometimes rewrites can be useful.

In other cases, your system might be doing just fine, and it needs parts of it re-written to be more scalable/efficient/whatever.

It always depends on the specific circumstance you're in. When deciding between the options, it makes a lot of sense to think through these things for a while and make sure you're doing it for the right reasons.

[dahart]

I don’t doubt it has happened somewhere, but I’ve never seen the mythical complete rewrite that was awesome and saved time and did it better the second time. Unless you’re talking about rather small projects of one or two people rewriting something in one month...

In three different large teams (~100 people) during my career, I have witnessed the other kind of rewrite. People forgot how many things were working right, and had started to focus only on the warts. They overestimated their ability to redo what they’d done before, and underestimated how long it would take. Why does anyone assume a multi-year project will go any faster the second time? You need a lot of evidence for that, and I’ve never seen any. In all cases, the rush to rewrite quickly caused people to cut corners and introduce new design mistakes, ultimately ending up with something that was only marginally better after a heavy cost of several years’ development. In all cases I’ve seen, the people in charge admitted regretting the decision to rewrite code and told me they wished they’d done it more piece-meal.

Just a data point, but I have to wonder how often a clean rewrite actually happens. I’m looking for the link now, but I remember reading on Wikipedia that it’s estimated that 30% of software globally is late and over budget. I suspect that rewrites are more affected by Planning Fallacy than the first time through, it’s easy to assume you can do better. https://en.m.wikipedia.org/wiki/Planning_fallacy

[james_s_tayler]

A big piece of enterprise software I've worked on did a full rewrite successfully. This was a long time before I joined, but the original product was written in Magik and apparently the only requirement was "make it work like magik" which I thought was pretty funny. It definitely was a success.

Though on the same product I came across a mildly hideous half-baked attempt at a UI framework re-write. I got the story on that and it was definitely one of the time-wasting regret stories.

Software is mostly just hard and expensive.