Concepts

The behaviour no single endpoint owns: settlement, money, quotes, idempotency, attribution and limits.

These pages describe behaviour that no single endpoint owns. The first two are the ones that cause a rewrite when they are discovered late.

An order settles after the call that created it. Read this before you design anything.

Decimal strings on the wire, integer minor units underneath. Getting this wrong loses money quietly.

A locked rate, single-use and short-lived.

What makes a retry safe, on both order creation and webhook handling.

Which identifier attributes a payment to an order, and why.

Request rate, order ceilings, and the 429 contract.

Which obligations are yours and which are ours.