[ChicagoDave]

There's a Domain-Driven Design pattern that encapsulates this entire problem. First, never even think about rewriting an entire system. You will likely fail. Not because you're not smart and capable, but because the business won't be patient enough to allow you to do it properly. And they'd be right not to be patient. They have things to sell and customers to support...today.

That's why Eric Evans came up with the Autonomous Bubble pattern. You rebuild features one at a time and connect them to the old code through anti-corruption layers and translation layers. Over time, the older code will be set aside. In a year or two, the plug will have naturally been pulled on all of the older code.

So there's some truth to Spolsky's 2000 blog post. But it's not smart to maintain older code forever either. You have to be careful, thorough, and use the right tools.

[HenryBemis]

> They have things to sell and customers to support...today.

Deau ex Agile.. knock out one "thing" at a time and let's keep loading the backlog for the next features/etc to be upgraded/rewritten. Tbh in banking I see very few rewrites, most banks (that make their own applications) don't fix it unless it breaks down. They only bother in massive upgrades where modules are rewritten, or an application is replaced one module at a time.