"I don't understand payments." Now what?
Answer it out loud before you open anything. The value of the flags below is in comparing them to what you actually said — including whether you asked who uses it before naming what you would build it with.
A junior engineer on your team has been assigned the checkout payment step. Two days in, they say: "I don't understand payments. I think we need someone with payments experience before I can continue." They have read the provider's documentation home page and watched a video.
React to this
Say what you would question, what you would keep, and what you would need to know first.
The engineer's notes so far (illustrative): Unknowns: - payments - how does Stripe work - security stuff - what if it fails Done: - read the docs home page - watched "Stripe in 100 seconds" - installed the SDK Blocked: need someone who knows payments.
What it is really testing
Whether the candidate can turn an unknown into a specific question and a tiny experiment, and whether they can coach someone else to do it — the move is the same whether the unknown is theirs or a colleague's.