Tangentially, over my lifetime experience, I understand that QA Testing should be done on public (user) interfaces. Intermediate data marshalling or transport,

Tangentially, over my lifetime experience, I understand that QA Testing should be done on public (user) interfaces. Intermediate data marshalling or transport, eg kafka delivering data from one application to another, is a dev ticket but has no QA component. Just as QA doesn't look at the individual data structures and method access modifiers, there are technical tasks and processes that QA has no stake in, nor can they do anything but complicate a delicate system with additional instrumentation/hooks. Generally, developers will want instrumentation, which is a public interface that QA can test, but is not mandated by QA as part of design.