Stripe Interview Process 2026 — Rounds, Tips & Questions

Design a distributed rate limiter that works across 100 API servers. A user is allowed 1000 requests per minute.

Design Stripe's webhook delivery system. Stripe sends millions of webhooks per day to customer endpoints that can be slow, down, or buggy. Cover: at-least-once delivery guarantees, retry with exponential backoff, ordering guarantees (or lack thereof), how to handle a customer endpoint that is down for 24h, and the dead-letter strategy.

Design Stripe's fraud detection system. For every payment, you must decide accept/decline in under 100ms using hundreds of signals. Cover: feature engineering, real-time ML scoring, rule engine, and how you minimise false positives (declined legitimate payments).

Explain how Stripe handles exactly-once payment processing. A customer clicks "Pay" twice in quick succession. How does Stripe prevent double-charging? Walk through idempotency keys in the API, database-level constraints, and how the client should handle the case where the first request times out.

Design Stripe's subscription billing system (Stripe Billing). Customers are charged on recurring intervals (monthly/annual) in different currencies, with proration for plan upgrades. Cover: invoice generation, dunning for failed payments, and SCA (Strong Customer Authentication) compliance.

Explain the difference between synchronous and asynchronous API design using Stripe as an example. When does a charge complete immediately vs require a webhook? How do you handle the intermediate "pending" state in your database?

Explain PCI-DSS compliance requirements for handling card data. What is tokenisation? How does Stripe use it to ensure raw card numbers never touch customer servers? What are the implications for your API design?

Stripe is known for extremely high engineering standards ("move carefully and fix things"). Describe a time you pushed back on a deadline to ensure correctness. Was it the right call?

Explain idempotency keys in a payments API. What specific failure mode do they prevent, and how would you design the storage layer for them so they don't become a bottleneck?

Design a double-entry ledger system for tracking money movement between accounts. Why is this pattern preferred over simply updating a balance column, especially for auditability?