Mock system design interview at Robinhood
A live 45-minute round on a question reported in Robinhood 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.
Design a Stock Exchange
Match buy and sell orders in microseconds, in a strict and provable order, never lose a fill, and stay correct when the matching engine dies mid-trade.
You will not see the requirements, the numbers or the design before you start. That is the point.
What the Robinhood round is reported to look like
About an hour. Prompts are reported to be either trading-shaped, such as order entry or a stock quote service, or general infrastructure, often a distributed job scheduler.
What it weighs
- Execution guarantees: at-least-once or at-most-once, and how a duplicate run or order is prevented
- Durable state, and recovery when a worker or service fails partway through
- Correctness where money moves: orders, positions and payments that reconcile
The common mistake
Leaving the guarantee vague. Scheduler and order prompts are reported to turn on whether work runs at least once or at most once and what happens to it after a crash, so state the guarantee early and design for it.
From public interview guides and candidate reports, and Robinhood’s own interview guidance where it publishes any. Not endorsed by Robinhood. The interviewer is an AI running in that style; it is practice, not a prediction.
Start the round
The interviewer’s opening question is free. Answering it is part of Pro. See an example round and its debrief →
The 4 questions this round draws from
Each is reported in Robinhood interviews. Pick one to sit, or read its reference design and walk through a strong answer first.
- Design a Stock ExchangeMatch buy and sell orders in microseconds, in a strict and provable order, never lose a fill, and stay correct when the matching engine dies mid-trade.drawn
- Design LeetCodeRun untrusted code from strangers against hidden tests in a dozen languages, return a fair verdict in seconds, and survive 50,000 people submitting in the last minutes of a contest.
- Design Venmo80 M users paying friends instantly: 15 M transfers a day on a sharded double-entry ledger, funded and cashed out over slow bank rails.
- Design RobinhoodA retail brokerage: live prices to 3 M phones, 20 k orders a second at the open, every share and cent exact.
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