saadsalman.org · an interactive ride

Anatomy of a tap

I have spent most of my career on the issuing side of cards, at i2c and now at Keep, and the two seconds after a contactless tap are still my favorite piece of invisible infrastructure. So I built the journey as a ride. Your payment is the cart. The rails are real.

Or just scroll. The ride is the scroll.

$ € the tap shop terminal hello prove it's you acquirer card network token vault wallet taps only your bank BEEP the answer
0 ms
since the card met the field
1 / 7 0 to 20 ms

On the wire

The part nobody sees

The beep moved zero money

Everything on that ride was authorization. It reserved money and promised the merchant an answer, and that is all it did. After close the merchant batches the day's approvals, the acquirer submits them for clearing and the network nets every bank against every other bank overnight. Settlement lands a day or two later. The payment is really two events wearing one trench coat.

The gap between them explains most of the strange things cards do. It is why a hold can sit on your account for days after a hotel releases it. It is why a refund takes a week when the charge took a second. And it is why chargebacks can exist at all: until clearing happens, there is still time to argue.

Tuesday 6:12 pm
The tap
Authorization approved in about a second. Your bank places a hold. The merchant has a promise, not money.
Tuesday 11:30 pm
Clearing
The shop batches out. The acquirer submits the day's approvals and the network nets every bank against every other bank.
Wednesday or Thursday
Settlement
Your bank actually pays, the merchant's bank actually receives, and the hold becomes a posted transaction.

Follow the money

Who kept your 2,500 rupees

The merchant does not receive what you paid. A slice comes off the top and gets divided between everyone who ran a station on that ride. Drag the amount and watch the split.

PKR 2,500 what you tapped for
the full amount, fees exaggerated 8x so you can see them
Merchant keeps 98.0%
Interchange, to your bank 1.5%
Scheme fee, to the network 0.1%
Acquirer margin 0.4%

Illustrative rates on a typical 2% merchant discount rate. Every merchant's deal differs, and interchange varies by card type, category and geography. Interchange flowing to the issuer is why your card has rewards: the merchant is funding them.

The next time a terminal beeps at you, you will know it was never one thing. It was a radio handshake, a signature, a routing decision and a risk call, all riding the same rails. Authorization is a promise, settlement is the payment. Everything interesting about cards lives in the gap.