[david-gpu]

> while the new code base is much cleaner I'm convinced it would have been cheaper to just clean that code up in place

I saw one big rewrite from scratch. It was a multi-year disaster, but ended up working.

I was also told about an earlier big rewrite of a similar codebase which was a multi-year disaster that was eventually thrown away completely.

I did see one big rewrite that was successful, but in this case the new codebase very intentionally only supported a small subset of the original feature set, which wasn't huge to begin with.

All of this to say that I agree with you: starting from scratch is often tempting, but rarely smooth. If refactoring in place sounds challenging, you need to internalize that a full rewrite will be a few times harder, even if it doesn't look that way.

[hinkley]

I stayed at a place that was decades old, in part to decipher how they’d managed to get away with not only terrible engineering discipline but two rewrites without going out of business. I figured it would be good for me to stick around at a place that was defying my predictions for once instead of fleeing at the first signs of smoke. I’ve hired onto places that failed before my old employer did at least twice and I feel a bit silly about that.

I wasted a lot of my time and came away barely the wiser, because the company is spiraling and has been for a while. Near as I can figure, the secret sauce was entirely outside of engineering. If I had to guess, they used to have amazing salespeople and whoever was responsible for that fact eventually left, and their replacement’s replacement couldn’t deliver. Last I heard they got bought by a competitor, and I wonder how much of my code is still serving customers.

[RaftPeople]

> I saw one big rewrite from scratch. It was a multi-year disaster, but ended up working.

90% of large software system replacements/rewrites are disasters. The size and complexity of the task is rarely well understood.

The number of people that have the proper experience to guide something like that to success is relatively small because they happen relatively rarely.