Follow the money.
From checkout to settlement. Understand the participants, messages and money movements.
14 lessons · 73 minutes of reading and checks · Work at your own pace
The life of a card payment.
Follow a €100 purchase from the checkout to the merchant’s payout.
Read the lessonWho does what in a payment?
Gateway, processor, acquirer, network, issuer: roles before logos.
Read the lessonWhen a payment is challenged.
Chargebacks, refunds and the work that happens after a sale.
Read the lessonThe person and the payment
A successful identity check is not a promise to pay.
Read the lessonA card number with boundaries
Understand what a payment token replaces—and what it does not.
Read the lessonUndo the right thing
Release a hold or return a completed payment: first identify the state.
Read the lessonOne intention. One payment.
Treat a timeout as uncertainty, not permission to charge again.
Read the lessonA message is not yet evidence
Receive payment events without trusting every incoming request.
Read the lessonThree records. One explanation.
Connect orders, processing records and cash without hiding differences.
Read the lessonThe second route is still a payment
Improve resilience without turning uncertainty into duplicate attempts.
Read the lessonOne purchase, several currencies
Keep the rate, the amount and the conversion moment together.
Read the lessonSolvent is not the same as ready
Available funds have a location, a currency and a deadline.
Read the lessonRead the full price of acceptance
Interchange is one component, not the entire merchant bill.
Read the lessonA field has a meaning.
Richer messages help only when their information survives the journey.
Read the lessonPut one principle to work.
Choose a decision study. Before reading the next piece of evidence, explain what would change your view.
Open related practiceFollow the money.
From checkout to settlement. Understand the participants, messages and money movements.
Follow this route 02 / bankingOpen the system.
Accounts, permissions and bank payments. Understand what access does—and does not—mean.
Follow this route 03 / operationsKeep it moving.
Retries, records and reconciliation. Learn to diagnose the gap between a message and an outcome.
Follow this route 04 / riskQuestion the signal.
Evidence, identity and trade-offs. Build decisions that survive a second look.
Follow this route