Case Study: Redesign a Checkout Flow

Here is the prompt exactly as an interviewer would give it, cold, with a clock running: "This e-commerce app's checkout has a 68% cart-abandonment rate at the payment step specifically — not earlier in the funnel. You have 20 minutes. Walk me through how you'd approach redesigning it."

This is the single most common "live design" prompt in UI/UX interviews because it's cheap to set up, has no single right answer, and exposes exactly how a candidate thinks under pressure — whether they ask before they assume, whether they can generate more than one hypothesis, whether they can prioritize when they can't test everything, and whether they close with a real recommendation or a vague gesture at "cleaner UI." Every subject earlier in this track — the design process, research methods, information architecture, interaction and visual design principles, UX writing, usability testing, and metrics — exists to be pulled into an answer like this one, live, in real time.

What follows is a full worked answer to that exact prompt, structured the way you'd actually deliver it out loud in twenty minutes: not a lecture on checkout best practices, but one candidate's specific reasoning, specific numbers, and specific decisions, with each move explicitly tied back to a concept from an earlier subject. Read it as a transcript of a strong answer, not a checklist to memorize — the goal is to see how the moves connect, so you can make the same moves on a prompt you've never seen before.

The time budget this answer follows, roughly:

A candidate who spends more than four or five minutes on clarifying questions runs out of runway to sketch anything; a candidate who spends fewer than two skips the step interviewers weight most heavily. The budget above is a guide, not a script — but naming a budget out loud ("I'll spend a couple minutes on questions, then move to a diagnosis") is itself a good opening move, because it shows time-awareness under a stated constraint.