Mock system design interview at Shopify

A live 45-minute round on a question reported in Shopify interviews, run by an AI interviewer that asks one thing at a time, probes what you say, looks at your whiteboard, and weighs what that round is reported to weigh. It ends with a debrief: a score, what was strong, what was missing.

your question

Design a Payment System

Accept card payments for an e-commerce platform, move money correctly exactly once, and be able to prove it.

You will not see the requirements, the numbers or the design before you start. That is the point.

Walk through it first

What the Shopify round is reported to look like

60 minutes, practical and often commerce-shaped: flash-sale inventory, checkout, webhook delivery or notifications. Some loops also include a separate deep dive on a system you have built.

What it weighs

Stock under concurrent demand: reservations that cannot oversell in a flash sale
Asynchronous work done safely: retries, idempotency and at-least-once delivery, as with webhooks
Choices tied back to what merchants and their customers experience

The common mistake

Drawing services before the data model. Candidates report the model and the flow of data are where designs get stuck, and interviewers are reported to want concurrency, retries and consistency worked through rather than boxes on a diagram.

From public interview guides and candidate reports, and Shopify’s own interview guidance where it publishes any. Not endorsed by Shopify. The interviewer is an AI running in that style; it is practice, not a prediction.

Start the round

Timed · 45 minutesInterview conditions. The AI interviewer owns the clock; the AI Mentor is off.With the AI Mentor · untimedNo clock, and an AI Mentor beside you to ask when you are stuck.

The interviewer’s opening question is free. Answering it is part of Pro. See an example round and its debrief →

The 6 questions this round draws from

Each is reported in Shopify interviews. Pick one to sit, or read its reference design and walk through a strong answer first.

Design a Payment SystemAccept card payments for an e-commerce platform, move money correctly exactly once, and be able to prove it.
drawn
Design TicketmasterSell 60 000 seats in ten minutes to a million people at once: hold a seat while someone pays, never sell it twice, and keep the site up when demand is a hundred times supply.
Design an Online AuctionRun 50 million live eBay-style auctions: order every bid strictly per auction, push the price to watchers live, and close each auction exactly once.
Design AmazonA 500 M-product marketplace: product pages at 100 k views/s, carts that never lose an item, and Prime Day checkout without overselling.
Design a Price TrackerTrack 500 M products' price history and alert 50 M users when a price drops below their target, in time to buy.
Design a Webhook Delivery SystemDeliver 3 billion signed webhooks a day to a million customer endpoints, retrying for three days, without one slow endpoint delaying anyone else.

Other companies: Anthropic · Google · Meta · Amazon · OpenAI · Microsoft · Uber · DoorDash