Architecture & practice·Legacy systems and migration
everyone agrees it should be replaced, and everyone also agrees it is the only thing that knows the pricing rules.
Legacy system
Also calledlegacy code
A system that is still valuable, still running and no longer well understood by the people who maintain it. The useful working definition is code without tests, because that is what makes it frightening to change rather than merely old. Calling something legacy is not an insult and not an argument for replacement: it is a statement that changes to it carry unknown risk, which is a cost to plan for.