Visa's system design

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Visa · system design

Visa is a network, not a bank: it gets your bank's yes or no to the shop in seconds, and moves the real money later, netted, between thousands of banks.

+ The whole system in one paragraph

Visa connects four parties: you, the shop, the shop's bank and your bank. When you pay, VisaNet (Visa's network) asks your bank for a yes or no in seconds; if your bank doesn't answer in time, Visa answers for it. That yes is only a hold. The real money moves later, in daily batches, netted between the banks.

258B
transactions processed by Visa (fiscal 2025)[1]
~5B
Visa payment credentials, usable at 175M+ merchant locations (fiscal 2025)[1]
83,000
transaction messages a second Visa says it processes, at most (Oct 2025)[4]

In this lesson

4 chapters · ~10 min · a quick check in each

Everything is on this page — just scroll down ↓

Chapter 1 of 4

The whole system

1
Requirements

What it must do — and how well

The core of what Visa must do (yellow) and how well (blue). The 99.9999% uptime is Visa's own 2025 claim for today's network.

ⓘ Details & sources

Yellow = what the system must do. Blue = how well it must do it.[1][2][4]

Answer every tap inseconds, in 200+countries andterritories.Any card from anybank works at any of175M+ shops.Move the real moneylater, nettedbetween thousands ofbanks.Keep the real cardnumber out of shops'hands.Never leave a shopwithout an answer,even if a bank isdown.Banks must answer in10 seconds (5 inEurope), or Visaanswers.Visa says: 99.9999%uptime, fullredundancy (2025).Score fraud inmilliseconds,without blockinggood payments.
2
Architecture

Four parties and one network

Top: the live path that answers a tap in seconds (you, the shop, both banks and VisaNet). Bottom: the files that move the real money later. Dashed means our model.

ⓘ Details & sources

Top: the live answer, in seconds. Bottom: the money, later, in files. Click any piece; play a flow.[1][2][5]

Watch it happen:
VisaNet · authorization, live (seconds)VisaNet · clearing + settlement, later (files)tap12auth request2score it33yes or no?4clearing filenetnet to payYoucard or phone walletMerchantthe shop's terminalAcquirerthe shop's bankToken vaulttoken → card numberRisk scoreAdvanced AuthorizationCard historyprofiles per accountmodelV.I.P. Systemroutes every requestStand-Inanswers for the bankIssueryour bank: yes or noBASE IIclearing, in filesSettlementone net total per bank
clientserviceworkerdatabaseexternal dashed border = simplified model
12345
Step 1 of 5

You tap a card or a phone. The terminal builds an authorization request: the card, the amount, the shop.

3
Side by side

Two speeds: the answer now, the money later

Visa's key decision: split the answer from the money. An approval is only a promise and a hold, made in seconds; the money moves later, in batches, netted between banks.

ⓘ Details & sources

Authorization is a promise in seconds; clearing and settlement move the money, in files, later.[1][2]

Authorization — nowOne message each way, per paymentYour bank answers in seconds (10 sdeadline)If it can't, Stand-In answers for itResult: a hold on your account, no moneymovesvsClearing + settlement — laterFiles of records, in batches (BASE II)Netted into one total per bank, per dayReal money moves between the banksVisa guarantees it if a bank fails to payApproved is a promise. Settled is themoney.
Quick check

Visa processed 258B transactions in fiscal 2025. About how many is that per second, on average?

Pick one — or just keep scrolling, it's not graded.

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  1. 2Authorization
  2. 3Moving the money
  3. 4Growth & failures
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