Design a Payment Processing Service (Merchant to Payment Provider)

Company: OpenAI

Role: Software Engineer

Category: System Design

Difficulty: medium

Interview Round: Technical Screen

Quick Answer: This system design question evaluates a candidate's ability to model a distributed payment processing service that coordinates authorization, capture, and settlement between merchants and external payment providers. It tests reasoning about correctness guarantees under network failure, idempotency, and reconciliation, common concerns for high-throughput financial systems. The question probes conceptual understanding of distributed transaction integrity as well as practical architectural trade-offs.