Single word for (request, response) pair? (casual words ok)

I'm looking for an unambiguous word (or expression) for referring to a question and a corresponding answer as a single entity.

The word should express that no more and no less than 1 question and 1 answer is covered, and that they correspond to each other.

The terms "request, response" may be technical jargon but I'm looking for a general word (it may be technical or not).

(In case this should be obvious, please merge this to ELL, I'm not native.)

Solution 1:

Exchange or interchange might work in the absence of better words.

Solution 2:

Just call it a Transaction if you're not working with databases otherwise it can get confusing. I can also suggest Discourse but it may be a little far fetched.

I also want to add handshake as in a WebSocket Protocol Handshake

Solution 3:

Well, how about Q&A?

Q and A
noun Informal.
an exchange of questions and answers.

Also, Q&A.

If you are looking for variable names, you could always write QnA or QA or QandA or something.