前一段时间完成了一个基于生物识别技术的支付产品方案设计。该方案旨在通过生物特征识别（如掌静脉扫描）实现无需手机的便捷支付体验，为用户和商户提供更加安全、高效的支付解决方案。经过对敏感信息的脱敏处理，我将这个方案的核心设计理念、系统架构和关键流程记录下来，希望能为对类似技术感兴趣的读者提供一些参考和启发。本文将详细介绍该支付产品的目标、核心功能、系统架构以及交互流程，展示如何将生物识别技术与支付系统有机结合，打造一个既安全又便捷的支付生态系统。

在技术快速迭代的今天，生物识别支付代表了未来支付方式的重要发展方向之一。通过这篇文章，我希望能分享这一领域的一些思考和实践经验。

Biometric-Based Payment Product

1. Project Overview

This project aims to provide an innovative, convenient, and secure payment solution for users, allowing them to make payments without a phone using biometric features (such as palm vein scanning). The product will integrate payment API and biometric capture technology from a partner vendor to deliver a new payment experience for users and an efficient and secure method of receiving payments for merchants.

2. Project Goals

• To provide users with a convenient way to make payments without a phone
• To enhance payment security and reduce the risk of fraud through multi-factor authentication
• To simplify the payment process and improve transaction efficiency
• To offer merchants a modern method of receiving payments with real-time settlement
• To comply with local payment regulatory requirements and data protection standards
• To ensure system scalability and high availability

3. Product Core Feature List

3.1 User Features:

• User account registration with multi-factor authentication
• Biometric feature (e.g., palm vein) capture and secure encryption
• Initiating payments by scanning biometric features at participating merchants
• Real-time payment notifications (via biometric capture device, APP, SMS, Email, WhatsApp Message)
• Detailed transaction history with advanced filtering (via App)
• Comprehensive user account management (card binding, password change, security settings)
• Emergency account freeze functionality

3.2 Merchant Features:

• Real-time payment processing and confirmation
• Automated refund processing with approval workflow
• Flexible settlement cycles (T+0, T+1) with detailed reporting
• Advanced transaction search and export capabilities
• Detailed settlement reports and reconciliation tools
• Merchant profile and branch management
• Custom payment limit settings
• Integration with existing POS systems

3.3 System Management Features:

• Centralized user account management with audit trails
• Real-time transaction monitoring and fraud detection
• Device health monitoring and remote management
• Configurable system parameters and business rules
• Comprehensive reporting with data visualization
• System performance monitoring and alerts
• Audit logging for all critical operations
• Automated backup and disaster recovery

4 System Architecture

To serve 500k users with room for growth, this system involves the following enhanced components:

• Biometric Capture Device: Secure biometric capture with encryption and matching capabilities
• User App: The main entry point for user registration, account management, transaction viewing, etc.
• User Backend System: core business logic processing center, responsible for user management, biometric data management, interaction with Tap API, transaction processing, security control, etc.
• Payment API: Used to process actual payment transactions, including fund deduction and settlement.
• Merchant Backend (Web): The main entry point for merchants to receive payments, view transaction records, etc.
• Admin Backend (Web): Used by system administrators to manage system, generate reports, etc.
• Job Service: Used for scheduled tasks, such as payment reconciliation，data compensation, etc.
• Database: Used to store user information, transaction records, etc.(maybe master-slave architecture)
• Message Queue: Used for asynchronous message processing, such as payment notification, etc.
• Cache Layer: Distributed caching for performance optimization
• Monitoring System: Real-time system monitoring and alerting

In order to ensure the system’s scalability and high availability, the system deployment is implemented as described below:

flowchart TB
    subgraph payment gateway
        Payment-Gateway[third-payment-gateway] 
    end

    subgraph Storage
        MySQL[RDS-MySQL] 
        Redis[Redis]
    end
    
    subgraph MessageQueue
        MQ[RabbitMQ]
    end

    subgraph backend
        BackendService[backend-service] -->|JDBC| MySQL
        BackendService -->|Redis API| Redis
        BackendService -->|API| Payment-Gateway
        BackendService -->|send| MQ
        Payment-Gateway -.->|async| BackendService
    end

    subgraph user
        App[App] -->|REST API| BackendService
        BiometricDevice[biometric-device] --> BackendService
    end

    subgraph merchant
        WebMerchant[Merchant-UI] -->Merchant-Service
        Merchant-Service-->|JDBC| MySQL
        Merchant-Service-->|Redis API| Redis
    end

    subgraph operation admin
        WebAdmin[Admin-UI] -->Admin-Service
        Admin-Service-->|JDBC| MySQL
        Admin-Service-->|Redis API| Redis
    end
    
    subgraph job
        Job-Service -->|JDBC| MySQL
        Job-Service -->|Redis API| Redis
        Job-Service -.->|consume| MQ
    end

5. Core Interactive Process

5.1 Registration

sequenceDiagram
    participant User
    participant App
    participant BackendService
    participant BiometricDevice

    User->>App: Initiate Registration Request
    App->>BackendService: Send Registration Request (User Information)
    BackendService->>BiometricDevice: Request Biometric Capture
    BiometricDevice->>User: Prompt User for Biometric Capture
    User->>BiometricDevice: Complete Biometric Capture
    BiometricDevice->>BackendService: Send Biometric Data
    BackendService->>Database: Store User Information and Biometric Information
    Database-->>BackendService: Return Storage Result
    BackendService-->>App: Return Registration Success Information
    App->>User: Display Registration Success

5.2 Link Bank Card

sequenceDiagram
    participant User
    participant App
    participant BackendService
    participant Tap as Payment API

    User->>App: Initiate Card Linking
    App->>BackendService: Request Card Linking Initiation (User ID)
    BackendService->>App: Instruct App to Present Payment's Secure Form
    App->>User: Display Payment's Secure Card Input Form
    User->>App: Enter Bank Card Details
    App->>Tap: Send Card Details Securely (via SDK or Payment Page)
    Tap-->>App: Return Card Token
    App->>BackendService: Send Card Token and User ID
    BackendService->>Database: Associate Card Token with User Account
    Database-->>BackendService: Return Association Result
    BackendService-->>App: Return Card Linking Success Confirmation
    App->>User: Display "Card Linked Successfully"

5.3 Payment

sequenceDiagram
    participant User
    participant BiometricDevice
    participant BackendService
    participant Tap as Payment API

    User->>BiometricDevice: Initiate Payment Request
    BiometricDevice->>BackendService: Send Payment Request (Device ID, May Contain Initial User Identification)
    BackendService->>BiometricDevice: Request Biometric Verification
    BiometricDevice->>User: Prompt User for Biometric Verification
    User->>BiometricDevice: Complete Biometric Verification
    BiometricDevice->>BackendService: Send Biometric Data
    BackendService->>Database: Query User Biometric Information
    Database-->>BackendService: Return User Biometric Information
    alt Verification Successful
        BackendService->>Database: Retrieve User's Card Token
        Database-->>BackendService: Return Card Token
        BackendService->>Tap: Initiate Payment Request (Amount, Card Token, Merchant ID, etc.)
        Tap-->>BackendService: Return Payment Result
        BackendService->>BiometricDevice: Return Payment Success Information
        BiometricDevice->>User: Display Payment Success
    else Verification Failed
        BackendService->>BiometricDevice: Return Payment Failure Information
        BiometricDevice->>User: Display Payment Failure
    end

6. Security and Compliance Considerations

6.1 Data Security

• End-to-end encryption for biometric data storage and transmission
• Strict access control mechanisms for sensitive data
• Separation of biometric data from user identity information
• Regular security audits and penetration testing
• Multi-layered security architecture with defense-in-depth approach

6.2 Compliance

• Adherence to payment industry regulations and standards (PCI DSS)
• Compliance with data protection regulations (GDPR or local equivalents)
• Implementation of comprehensive user privacy protection mechanisms
• Complete compliance audit trail to meet regulatory requirements
• Regular compliance reviews and updates

7. Performance and Scalability

7.1 Performance Metrics

• Transaction response time: Average <1 second, 99% of transactions <3 seconds
• System throughput: Peak capacity of 100+ transaction requests per second
• System availability: 99.99% uptime (less than 1 hour of unplanned downtime annually)
• Data consistency: Ensuring integrity and consistency of all transaction data
• Biometric matching accuracy: False acceptance rate <0.001%, false rejection rate <1%

7.2 Scalability Strategy

• Automated elastic scaling based on load patterns
• Capacity planning for 300% growth over the next 2 years

8. Implementation and Operations

8.1 Implementation Roadmap

• Phase 1: Core payment functionality development and testing (2 months)
• Phase 2: Merchant management system and settlement functionality (1 months)
• Phase 3: Pilot deployment and optimization (1 months)
• Phase 4: Full-scale rollout and continuous improvement (ongoing)

8.2 Operational Strategy

• 24/7 monitoring system with real-time alerts
• Automated deployment and rollback mechanisms
• Comprehensive logging and analytics system
• Detailed disaster recovery plan with regular testing
• Continuous performance optimization and capacity planning

写到最后

以上是这个项目的完整方案，该方案通过整合生物识别技术与支付API，为用户提供了一种无需手机即可完成支付的便捷方式。系统架构设计充分考虑了安全性、可扩展性和高可用性，能够支持大规模用户群体的使用需求。

通过实施这一支付解决方案，我们期望能够：

• 为用户提供更加便捷、安全的支付体验
• 为商户提供更加高效、可靠的收款方式

未来，我们计划进一步优化系统性能，扩展更多场景应用，如将生物识别支付技术应用于多个领域。同时，我们也将持续关注生物识别技术的发展，探索更多创新的支付解决方案，为用户和商户创造更大的价值。