A 30-field application form re-renders the whole page on every keystroke and the caret lags behind typing. It is implemented with one piece of state holding the whole form object. Fix it, and tell me what you would have done differently from the start.
Answer it out loud before you open anything. The value of the flags below is in comparing them to what you actually said.
The situation behind the question
An insurance quote form with conditional sections, cross-field validation, a repeating address block, and a "save draft" that runs while the user types.
What it is really testing
Whether the candidate understands where form state should live and what the platform already provides, rather than reaching for a library reflexively. The lagging caret is a specific mechanism — a controlled input whose value round-trips through a render — and they should be able to say so.