Building Correct Payment Infrastructure: Webhooks, Reconciliation, and Records (opens in new tab)

Payments code has a strange property: most of it is boring, and the boring parts are exactly where money goes missing. Webhook handlers, money arithmetic, reconciliation jobs — the unglamorous plumbing every team rebuilds, slightly wrong, at every company. After close to two decades working on payment systems, I kept running into the same three mistakes, each cheap to make and expensive to find. So I wrote three small, dependency-free, MIT-licensed tools that each fix one. This post walks thr...