A driver in New York finishes her last trip of the night and closes the Uber app. She opens her banking app. The $15 fare she just earned is already sitting in her checking account, available to spend. Uber does…
You are traveling in France. You sit down at a café and order a coffee. The bill is €5.00. Ten years ago, tapping a standard US-issued debit card would trigger a traditional cross-border flow. The card network would authorize the…
A practitioner’s notes on financial infrastructure At the close of the authorization flow, the Cardholder walked out of the Tokyo coffee shop (Merchant) with a $5 latte. The Ohio Credit Union (Issuer) executed a soft-post, reserving $5 on the Cardholder’s…
In the architecture of card payments, there is a hard, physical boundary that does not exist in almost any other domain of distributed systems. When a customer dips a card at a merchant terminal, the Visa or Mastercard network initiates…
A practitioner’s notes on financial infrastructure A coffee shop in Tokyo (Merchant) accepts a Visa card issued by a small credit union in Ohio (Issuer). They share no database, no API contract, and no direct network path. The Cardholder taps…
A coffee shop in Tokyo accepts a $5 Visa card payment. The customer taps their card. Within seconds: But the most important decision in the entire transaction did not happen at the terminal. It did not happen at the payment…
