When I see the NotWritablePrimary error code name, I assume it means not (writable primary) and I am wondering if one can have a primary which is not writable and whether such a primary would be suitable for the operation being issued, or for other operations. As well as whether one can have writable non-primaries.

I assume what the code is intended to convey is that only primaries are writable and the responding node is not a primary.

If so, the intent can be in my opinion more clearly communicated by using code name like NotWritableNotPrimary.