How to assess the level of a programmer in half an hour?

Question

C++ / C#

I understand that the question is idiotic. Today an employee from the customer should arrive, and I need to evaluate whether he can take a software module that we have not yet developed in support. C++ embedded systems. Moreover, it is necessary to approach responsibly and fill up if it does not pull, so that he himself understands this.
Usually I do the technical part of the interviews, but it's not half an hour at all. And at the interview it is not necessary to bring down, but it is necessary to evaluate. Plus there is a summary.
You can let some cppquiz decide, but this is cruel and will not give a real picture.

Answer 1

You ask for canonical basics (how the language works, addressing, inheritance and polymorphism), then for language features (memory freeing and "garbage collectors", etc.), then something about your module, etc. In half an hour, you can find out well at least whether a person knows how to read documentation and express his thoughts.

Answer 2

The customer simply wants to save money on our support.
In fact, it will turn into free consultations of this programmer.

Tell the customer that you will consult his programmer at a rate of two or more times more
You don’t even have to waste your time testing his skills
Especially for free