Mock system design interview at Airbnb

A live 45-minute round on a question reported in Airbnb 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 Airbnb round is reported to look like

45–60 minutes, product-shaped around the marketplace: booking and availability, listing search, messaging between guests and hosts, notifications or payments.

What it weighs

Booking correctness: no double-booking, and a booking request that is safe to retry
A data model that holds up as features, and then scale, are added
Edge cases and failure modes, not only the happy path
A realistic design that could be built, without needless complexity

The common mistake

Stopping at the happy path. Interviewers are reported to keep asking what happens when two guests want the same dates, a request is retried or a service stops answering, and a design that only works when nothing fails does not hold up.

From public interview guides and candidate reports, and Airbnb’s own interview guidance where it publishes any. Not endorsed by Airbnb. 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 9 questions this round draws from

Each is reported in Airbnb 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 a Notification SystemDeliver push, email, SMS and in-app notifications to hundreds of millions of users: the right channel, once, on time, and never at 3 a.m.
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 Search AutocompleteSuggest the top ten completions after every keystroke, in under fifty milliseconds, from what the world searched for in the last hour, without suggesting anything that gets you in the newspaper.
Design AirbnbSearch 7 M listings by place, dates and price, book a stay without ever selling the same night twice, and keep calendars in sync with hosts’ other platforms.
Design Apache AirflowSchedule and run twenty thousand data pipelines as dependency graphs, each run tied to a slice of time, so a failed night can be retried or a year backfilled safely.
Design an A/B Testing PlatformRun 500 experiments at once on 300 M users: sticky variants in microseconds, exposure logging, and confidence intervals teams can trust.
Design a Fraud Detection SystemAllow, block or challenge 10,000 card payments a second in under 100 ms, then learn from chargebacks that arrive months later.
Design a Flight Booking SystemAnswer 50 M searches a day from 20 slow, metered suppliers through a fare cache, then book seats you do not own, exactly once.

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