Mock system design interview at Stripe
A live 45-minute round on one of the questions reported in Stripe interviews, run by an AI interviewer that asks one thing at a time, probes what you say, and weighs what that round is reported to weigh. It ends with a debrief: a score, what was strong, what was missing.
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 diagram before you start — that is the point.
What the Stripe round is reported to look like
45–60 minutes, typically money-adjacent: correctness, idempotency and reconciliation over raw scale.
What it weighs
- Exactly-once effects, idempotency keys and retries
- Ledger and state-machine design, including the unknown-outcome case
- API design and the developer experience of the thing you are building
- Reconciliation and what happens when an external system disagrees with you
The common mistake
Optimising for throughput when the question is about never losing or double-charging a payment.
From public interview guides and candidate reports, not from Stripe. The interviewer is an AI running in that style; it is practice, not a prediction.
Start the round
Other companies: Anthropic · Google · Meta · Amazon · OpenAI · Microsoft · Uber · NVIDIA