I’ve worked in payment systems for a long time, and one common theme is that they make a lot of 3rd party API calls. For example, there are numerous payment networks and banks, fraud and risk checks, onboarding and KYC/KYB (Know Your Customer/Business) services, and more. And then there are the inbound calls as well, such as webhooks and callbacks from integration partners, e-commerce stores, and other outside interactions.
