[xeonoex]

I think that's too simple of a case to really make an argument either way. Just return a Some/None or Optional. Null is ok too, but not the best (it's baked in to most languages already though). But at a higher level, if the program expected something, it may be an exception. Let's consider another case. What if you made the request and your session got terminated? That will be an exception too, and I don't think anyone will add that to the result type.

I feel like encapsulation means that functions often should throw errors, because the small, one responsibility functions shouldn't have knowledge of control flow. For example, division. Anytime you divide, you might try to divide by 0. That's an exception. The / operator returns a number or throws an exception. Who would use a TryDivide function? What would it solve? The same error might be an exception in one scope, and expected in another.

I get that exceptions can be expensive, but they should be rare. Saving time on the pre-check for an exception might save more time than the rare exception. I would never throw an exception strictly for control flow, but avoid exceptions is a bad idea IMO.

But the line is very blurry.