What it actually takes to take a payments feature from idea to production: scoping, integration choices, money-movement edge cases, compliance gates, and the launch checklist that keeps you out of an incident review.
Every other course explains how payment systems work. None teaches how to build and ship inside them. This is the craft course: idempotency, ledgering, reconciliation, and the launch gate, where money has no undo.
We scope the unhappy paths first, choose between build, buy, and orchestrate, design a ledger that stays correct under failure, and clear the compliance gates that block launches, ending with a pre-launch checklist for money-movement features.
Payments features fail differently from the rest of your product because a confirmed money movement cannot be reversed, only compensated. This lesson covers what that constraint changes about how we build, model state, and reason about errors.
Partial captures, refunds, disputes, and retries belong in the spec, not the postmortem. This lesson shows how to enumerate the money states that go wrong before you write a line of code.
A practitioner's decision framework for choosing between building your own payment stack, buying a single PSP, or running an orchestration layer, driven by the questions that actually move the answer.
How to build a double-entry ledger that survives crashes, concurrent double-spend attempts, and money that settles days after the user clicks pay.
Why retries and at-least-once webhooks quietly double-charge customers and corrupt your ledger, and the concrete patterns that stop it: idempotency keys, dedup tables, and signature-verified handlers.
Your ledger records intent; the rail records what actually moved money, and they almost never line up the same day. This lesson covers how to reconcile the two and design for the gap between authorization and cash in the bank.
How to keep PCI scope small, where KYC and AML actually sit in your build, and the one question that decides whether you need a money transmitter license.
How to test a payments product when the bug is a missing dollar, not a 500 error: drive the sandbox through the failure paths, prove your ledger reconciles, and inject chaos before production does.
How to instrument money movement so you see breakage before customers do, and how to run an incident when the thing that broke is a payment.
A concrete gate for clearing a payments feature to production: the environment, ledger, idempotency, reconciliation, compliance, and rollback checks that must be green before real money moves.