Virtual Card System Architecture: Issuance, Authorization, Settlement & Risk Control
Deep dive into the financial technology engine behind WasabiCard
1. From Card Issuance: Core Value of Virtual Card Systems
In traditional financial systems, issuing a bank card requires coordination between banks, clearing networks (Visa/MasterCard), and payment processors. In today's digital finance era, virtual cards are becoming a crucial component of financial infrastructure.
WasabiCard is a next-generation virtual card and payment system built on this trend, not just a "card issuance platform" but a complete financial ecosystem integrating SaaS + PayFi + DeFi:
- Multi-BIN, multi-channel, multi-currency support
- Covers virtual cards, physical cards, and corporate cards
- Integrated with stablecoin deposits and on-chain settlement
- Built-in risk control and authorization engine for second-level transaction verification
- API SaaS integration for B2B enterprises
Make card issuance as simple as deploying an app, make payments as flexible as sending transactions.
2. Overall System Architecture: Five-Layer Design
WasabiCard's system architecture can be summarized as a five-layer model:
โโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโ โ 1. ๆฅๅ ฅๅฑ๏ผAPI Gateway๏ผ โ โ ๅๆทใๅนณๅฐใ้ฑๅ ๆฅๅ ฅๅ ฅๅฃ โโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโค โ 2. ๅบ็จๅฑ๏ผCore Service๏ผ โ โ ๅๅก / ๆๆ / ๆธ ็ฎ / ้ฃๆง / ้็ฅ โโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโค โ 3. ่ต้ๅฑ๏ผSettlement Engine๏ผโ โ ้ฑๅ ใ่ดฆๆทใDeFiๆตๅจๆงๆฑ โโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโค โ 4. ๅไฝๅฑ๏ผBIN & Network๏ผ โ โ Visa / Master / BIN Sponsor โโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโค โ 5. ๅ่งไธๅฎก่ฎกๅฑ๏ผCompliance๏ผโ โ AML / KYC / ไบคๆ็ๆต โโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโ
These five layers each handle independent functions while coordinating through internal message queues and event buses, ensuring high concurrency and system stability.
3. Card Issuance Logic: From BIN to User Wallet Lifecycle
The virtual card lifecycle begins with BIN (Bank Identification Number). In WasabiCard's system, each virtual card is generated through these steps:
1. BIN Selection
System automatically matches available BINs based on user region, currency, and card type (virtual/physical/corporate).
Example: European users might use Visa EU BIN, Southeast Asian users might be assigned MasterCard SEA BIN.
2. Card Number Generation
Card numbers are generated within the BIN range through encryption algorithms and bound to unique cardholder_id in the database.
3. Card Activation & KYC Verification
Some BINs require cardholder verification (SumSub/Onfido integration). WasabiCard provides modular abstraction, allowing merchants flexible KYC process selection.
4. Account Association
Each card is bound to a virtual account for deposits, debits, refunds, and settlements. The account connects to Wasabi Settlement Engine, supporting on-chain/off-chain dual-track settlement.
5. Card Distribution & Display
System returns card number, expiration date, and CVV to merchant via API for secure frontend display. (CVV visible only on first call, encrypted storage.)
Key Point: Card issuance is fully automated, average issuance time < 3 seconds.
4. Authorization Logic: First Line of Risk Control
Authorization is a core component of virtual card systems. When users initiate transactions at merchants, the network layer (Visa/Master) sends a request to Wasabi's authorization engine:
"Is this transaction allowed?"
Wasabi's authorization system executes multi-dimensional verification in real-time:
| Verification Dimension | Logic Description |
|---|---|
| Cardholder Status | Is card activated, is it frozen |
| Balance Check | Is virtual account balance sufficient |
| Risk Rules | MCC, country, amount, frequency limits |
| Blacklist Detection | Merchant, device, IP, country-level risk lists |
| Exchange Rate | For cross-currency transactions, real-time conversion and fee deduction |
System typically returns:
- APPROVED (Approved)
- DECLINED (Declined)
- REFER (Manual Review Required)
Average authorization response time ~150-200ms, ensuring smooth user transaction experience.
5. Settlement Logic: How Funds Flow
Authorization is just "pre-hold", settlement is the actual fund settlement phase. WasabiCard's settlement logic follows international card network procedures with technical optimizations.
1. Settlement Path
็จๆทๅก่ดฆๆท โ Wasabi่ต้ๆฑ โ ็ป็ฎ้ถ่ก่ดฆๆท โ Visa/Master โ ๅๆทๆถๆฌพๆน
2. Key Mechanisms
- T+0/T+1 Dynamic Settlement:Different BINs and merchant types support different settlement cycles.
- Cross-Border Settlement Smart Matching:System automatically identifies cross-currency transactions and selects optimal exchange rate channels.
- Transparent Fees & Exchange Rates:All transactions return fee, cross_border_fee, settle_amount fields in real-time.
3. On-Chain Settlement Innovation (PayFi Model)
In Wasabi's on-chain ecosystem, fund settlement supports stablecoins (USDT/USDC).
- After user deposits, on-chain addresses are generated, funds automatically mapped to settlement pools.
- Unused balances automatically enter DeFi liquidity pools to earn yield.
- During transactions, system instantly withdraws corresponding funds from yield pools for payment.
This means: Every payment is made on "living money", maximizing capital efficiency.
6. Risk Control Logic: System Security's "Nerve Center"
The biggest challenge in virtual card systems isn't issuance, but "preventing risk control abuse".
WasabiCard's risk control system has three layers: Real-time Risk Control (instant decline) + Behavioral Risk Control (user profiling) + Model Risk Control (AI detection)
1. Real-time Risk Control (Rule Engine)
Through Rule Engine, instantly determine if transactions are legitimate:
- Blacklist MCC rejection (e.g., gambling, adult, self-service gas)
- High transaction frequency triggers rate limiting
- Large cross-country transactions automatically trigger manual review
2. Behavioral Risk Control (Behavioral Analysis)
Build behavioral models by tracking user transaction times, merchant types, device fingerprints.
If transaction behavior deviates from normal patterns (e.g., user suddenly spending in Africa after Japan), system instantly freezes transaction.
3. Model Risk Control (AI Detection)
Based on machine learning model training:
- Input features: Amount distribution, MCC, geography, time, failure count
- Output: Suspicious transaction score (0-100). If risk value exceeds threshold, automatic decline or secondary verification.
Additionally, Wasabi's risk engine integrates with external compliance services (e.g., Chainalysis/TRM Labs) to monitor crypto fund source compliance, preventing AML and sanctions risks.
7. API Integration & Enterprise SaaS Architecture
WasabiCard provides complete SaaS + API integration capabilities for enterprises, enabling integration within days.
Core Interface Modules:
| Module | Main Interfaces |
|---|---|
| Issuance | /card/v2/create, /cardType/list |
| Authorization | /transaction/authorize, /transaction/refund |
| Settlement | /settlement/status, /balance/check |
| Risk Control | /risk/query, /limit/update |
| Wallet | /wallet/deposit, /wallet/withdraw |
Technical Features:
- RESTful design + JWT security authentication
- Fully async architecture supporting high concurrency
- Real-time webhook transaction status push
- Enterprise-level SLA support and log tracking
Merchants can directly issue branded cards, top up balances, monitor transaction status via API, building their own financial product ecosystem.
8. Compliance & Globalization: Wasabi's Security Moat
In virtual cards, technology is just the prerequisite, compliance is the survival line.
WasabiCard partners with multiple international licensed institutions, covering BINs and settlement networks in Europe, Southeast Asia, Middle East, and more.
- KYC/KYB systems (Sumsub integration)
- Real-time AML monitoring
- OFAC/EU Sanction list comparison
- GDPR data security compliance
- PCI-DSS payment security certification
Additionally, WasabiCard has established distributed fund account system ensuring:
- User asset segregation (User-level Ledger)
- Multi-currency fund visualization
- Full-chain encryption and multi-signature
This makes Wasabi one of the few virtual card platforms capable of two-way passage between Web3 and traditional finance.
9. Future Outlook: From Card Issuance to Financial Ecosystem
Virtual cards' value lies not just in "issuance" but in reshaping the entire financial infrastructure.
WasabiCard's next phase will focus on three major directions:
1. Financial Modularization (Finance as a Service)
Open APIs allowing more enterprises to create their own card issuance and settlement systems within Wasabi ecosystem.
2. PayFi Networkization
Through decentralized settlement nodes (PayFi Nodes), achieve more efficient cross-border fund settlement and yield distribution.
3. Global Fund Flow Visualization
Build real-time Settlement Graph, allowing enterprises to clearly see each fund flow, yield source, and risk status.
Future finance is no longer "bank services" but "API services". WasabiCard is making this vision a reality.
10. Conclusion: Virtual Card System's Essence is "Trusted Liquidity"
Issuance is the entry, authorization is security, settlement is flow, risk control is the moat. These four modules form the skeleton of modern virtual card systems.
WasabiCard, by integrating on-chain finance (DeFi) with traditional payment networks (Visa/Master), achieves intelligent and yield-generating financial systemsโmaking "every payment grow".
WasabiCard: Making virtual cards not just payment, but an engine for asset flow.
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