#payments

15 payments interview questions, asked at Stripe, Airbnb, OpenAI and 8 more companies. Last asked Oct 2026.

Make a charge-then-record payment flow safe against crashes and retriesCodingA backend first charges a customer through an external payment provider and then writes the payment to its own database. You are shown code like this (in Java or Python) and asked…
Last asked Oct 2026
Split-tender payments with gift cards, surcharges and refundsCodingAt a retail point of sale one purchase can be paid with several methods, for example part on a gift card and the rest on a credit card (a split-tender transaction). Write the code…
Last asked Oct 2026
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Design a payment systemSystem designAccept card payments for merchants: authorize, capture, settle with card networks, and reconcile, never charging twice or losing money.
Last asked Oct 2026
Design a digital game store like SteamSystem designDesign a digital game distribution platform like Steam. Players use a desktop client to browse a store, buy games, see what they own in a library, and download, install and update…
Last asked Sep 2026
Design a payments ledgerSystem designDesign the double-entry ledger behind a payments API: money movements must never be lost or applied twice.
Last asked Aug 2026
Design an idempotent double-entry ledger serviceSystem designDesign a ledger service that records money movements for merchants as double-entry transactions and answers balance and history queries. Cover the data model, making writes…
Last asked Aug 2026
Design a reliable job schedulerSystem designDesign a service that runs jobs at scheduled times at large scale, such as payment jobs that must run on time and exactly once in effect. Cover storing schedules, finding jobs…
Last asked Aug 2026
Refund allocation across prioritized payment methodsCodingA customer's order was paid with one or more payments, and some of them may already have been partly refunded. Implement a function that splits a new refund across those payments…
Last asked Apr 2026
Transaction fees from a CSV of paymentsCodingYou get payment transactions as a CSV string. Compute the fee for each one and the total fees per user. The rate depends on the payment type and provider and on the transaction's…
Last asked Apr 2026
Design a digital game store backendSystem designDesign the backend of an online store that sells digital games: players browse a catalog, buy games, and own them afterwards. Focus on the purchase: taking the payment, granting…
Last asked Dec 2025
Design a basic credit card systemOO designDesign the classes for a simple credit card system: cards and accounts, a credit limit, purchases, payments and the balance. Show how a purchase is authorized against the limit…
Last asked Oct 2025
Design a wallet with holds and payoutsOO designDesign and code a wallet for a rental platform. Users keep a balance; money can be put on hold (for example when a booking is made), then captured or released, and hosts receive…
Last asked Sep 2025
Split a monolithic wallet service into microservicesSystem designA digital wallet runs as one monolith. Plan its move to microservices: how you choose service boundaries, keep the data consistent across services during and after the split…
Last asked Sep 2025
Keep a shared payment account correct under concurrent paymentsSystem designTwo people share one online payment account and pay with it at the same moment. How do you make sure the balance never goes wrong? Answer from the API side (idempotency, request…
Last asked Jul 2025
Design a merchant lending systemSystem designOffer business loans to merchants based on their payment history, then repay automatically by withholding a share of each day's sales.