Some people know how to program. Other people dedicated years to the study of computer architectures, first order logic, distributed systems, fault tolerant systems, etc ...

In my opinion, computer science and engineering is not about just making the code you're told, it's about questioning whether that code needs to be done in the first place, and if so, how.

Most software development is not done, or meant to be done as an engineering discipline. It is far more often a craft. That said, it depends on the project, environment, company and legal requirements.

For that, hire a programmer. Need a dependable architecture for mission critical software? You get the point ...

Define mission critical? Can be down for a 15 minute update once a week? Most have transparent updates? Should be up most of the time? Must be up durring East coast business hours?

It still depends.