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Tue, Jun 9, 20267:00 PM - 8:00 PM PDTSession ended

Payment Systems

Exactly-once processing, settlement, and reliable webhooks

About this session

A 90-minute live deep-dive into building a Stripe-like payment system: payment initiation and authorization, exactly-once processing under network timeouts, PCI-safe tokenization, daily batch settlement, and reliable webhook delivery to flaky merchant endpoints. Great prep for Stripe, PayPal, and OpenAI money-movement interviews.

Course Syllabus

Course Overview

Format:
Live Zoom, 90 minutes (75 min teaching + 15 min Q&A)
Audience:
Mid-level to Staff+ engineers prepping for payments/fintech interviews
Prerequisite:
Comfort with transactions, idempotency, and message queues

What You Will Learn

  1. Design payment initiation, authorization, and real-time status tracking at 10,000 QPS.
  2. Guarantee exactly-once processing when a timeout hits after bank approval but before you record it.
  3. Keep card data safe with tokenization — support recurring charges without storing raw PANs.
  4. Build reliable webhook delivery with retries and backoff for merchant endpoints that go down.
  5. Handle partial settlement failure: customer debited but merchant payout fails.

What This Course Is NOT

  • Not a fraud/ML-risk course — we focus on the money-movement path
  • Not a deep dive on card-network protocols — banks are treated as an external dependency

Pre-Class Preparation (24 hours before)

Read the problem statement only (10 min):

Design a Stripe-like payment system that lets merchants submit payment requests, lets customers complete payments with a stored method, provides real-time status tracking, and settles all authorized payments once daily — at up to 10,000 QPS sustained throughput.

Think about (don't research yet):

  • What key makes a retried charge safe to replay exactly once?
  • What happens to the customer's money if settlement to the merchant fails?
  • How do you notify a merchant whose webhook endpoint is down for an hour?

Come to class with an idempotency-key scheme sketched out.

Lecture: author of showoffer

Jay

ShowOffer Coach

12+ years of experience building AI/ML infrastructure, payment platforms, and large-scale distributed systems. Tech lead for fan-out architectures powering millions of product queries and high-throughput payment workflows at scale.

Reviews

5.0(1)

  • Reviewer 0RYZ

    Jun 15, 2026

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