Introduction: The Hard Parts

Suppose you have reached the part of the interview where you discuss failures and difficult cases.

The resources are named. The operation list is on the board. One create operation has a request, response, and ordinary validation errors.

Then the interviewer changes the question:

"What happens if the caller sends the payment twice?"

The interviewer is testing how the existing operation behaves when the outcome is uncertain.

That is the subject of this chapter. Chapters 2 and 3 established what callers can request and how results can be delivered