Myth: if it's legacy, you do not need to comprehend it

A software engineering myth says that if a system is legacy, you do not need to comprehend it. Instead, you are often advised to wrap it and work with it through a facade without worrying what happens underneath the black box.

But, as long as you still need something from your legacy system, you still need to understand at least that something. After all, many companies can live out of charging support even if they give you a free black box system. You do not need to modify that system, but you still need to figure out how it does what it does.

Take something like JBoss. If you use it, you might not consider it legacy, but you likely work with it through the advertised facade. But, once you do anything meaningful with it, you get to learn what it takes to understand what happens in its dungeons.

The only system that does not require comprehension is a dead one.

Instead of pretending that you avoid comprehension, better get good at digging up what you need fast and cheaply. It's more profitable. And more realistic.