alt Hacker News> I don't think it's necessarily a given that "no document" and "no owner" should be handled identically (e.g., searching for the updated document to try again vs. returning an operation-not-allowed error).
If you care whether a document exists or not, you should use an API that exclusively tells you that instead of expecting everything related to documents telling you if the document exists or not. Otherwise you’re overloading the meaning. A non existent document has no owner. An API to fetch the owner of the document should not care if it exists or not, it does not matter.
As I said, that sounds like a recipe for potential TOCTOU errors.
But again, this was an off-the-cuff example that I explicitly described as contrived from the start. I could probably flesh it out to make more sense, but I think it'd be easier just to refer to sibling comments rather than bikeshed this to death.