It's a question of framing. Nothing is ever over- or under-engineered. It's over- or under-engineered for a purpose. What that distinction recognizes is that i

It's a question of framing. Nothing is ever over- or under-engineered. It's over- or under-engineered for a purpose. What that distinction recognizes is that it's possible for something to have been well-engineered at one time, while still being over-engineered today. Header files in C and C++ are an example of this phenomenon. They solved a very real problem with technical constraints from 40, 50 years ago, both in terms of computers' capabilities and compiler technology, but, since those problems don't exist anymore, they function as over-engineering.