Architecture
Understanding the technical architecture of b402Layer Payment Infrastructure.
System Architecture
┌─────────────────────────────────────────────────────────────┐
│ Client Applications │
│ ┌──────────┐ ┌──────────┐ ┌──────────┐ ┌──────────┐ │
│ │AI Agents │ │ DApps │ │ CLI │ │ SDK │ │
│ └──────────┘ └──────────┘ └──────────┘ └──────────┘ │
└─────────────────────────────────────────────────────────────┘
│
▼
┌─────────────────────────────────────────────────────────────┐
│ API Gateway Layer │
│ ┌──────────┐ ┌──────────┐ ┌──────────┐ │
│ │ REST │ │WebSocket │ │ GraphQL │ │
│ └──────────┘ └──────────┘ └──────────┘ │
└─────────────────────────────────────────────────────────────┘
│
┌─────────────────────┼─────────────────────┐
▼ ▼ ▼
┌───────────────┐ ┌───────────────┐ ┌───────────────┐
│ Payment │ │ Webhook │ │ Analytics │
│ Service │ │ Service │ │ Service │
└───────────────┘ └───────────────┘ └───────────────┘
│ │ │
└─────────────────────┼─────────────────────┘
▼
┌─────────────────────────────────────────────────────────────┐
│ Data Layer │
│ ┌──────────┐ ┌──────────┐ ┌──────────┐ │
│ │PostgreSQL│ │ Redis │ │ Queue │ │
│ └──────────┘ └──────────┘ └──────────┘ │
└─────────────────────────────────────────────────────────────┘
│
▼
┌─────────────────────────────────────────────────────────────┐
│ Blockchain Layer (BNB Chain) │
│ ┌──────────────┐ ┌──────────────┐ ┌──────────────┐ │
│ │B402 Payment │ │ Escrow │ │ Token │ │
│ │Contract │ │ Contract │ │ Contracts │ │
│ └──────────────┘ └──────────────┘ └──────────────┘ │
└─────────────────────────────────────────────────────────────┘Core Components
1. API Gateway Layer
The entry point for all client requests.
Features:
Request routing and load balancing
Authentication and authorization
Rate limiting and throttling
Request/response transformation
API versioning
Technologies:
Node.js + Express/Fastify
JWT authentication
Redis for rate limiting
2. Payment Service
Handles all payment-related operations.
Responsibilities:
Create payment requests
Process transactions
Monitor blockchain events
Update payment status
Handle refunds
Key Features:
Automatic retry logic
Transaction confirmation tracking
Gas price optimization
Multi-token support
3. Webhook Service
Manages webhook notifications for payment events.
Features:
Event subscription management
Reliable delivery with retries
Signature verification
Event logging and replay
Delivery Guarantees:
At-least-once delivery
Exponential backoff retry
Dead letter queue for failed deliveries
4. Data Layer
Persistent storage for application data.
PostgreSQL:
Payment records
User accounts
Transaction history
Webhook configurations
Redis:
Session management
Rate limiting counters
Real-time payment status
Cache layer
Message Queue:
Asynchronous job processing
Webhook delivery queue
Blockchain event processing
Payment Flow
Step-by-Step Process
1. Client Request
↓
2. Create Payment Record (PostgreSQL)
↓
3. Generate Payment ID
↓
4. Create Smart Contract Transaction
↓
5. Submit to BNB Chain
↓
6. Monitor Transaction Status
↓
7. Wait for Confirmations (12 blocks)
↓
8. Update Payment Status
↓
9. Trigger Webhooks
↓
10. Notify ClientDetailed Flow Diagram
┌─────────┐ ┌─────────┐
│ Client │ │ Service │
└────┬────┘ └────┬────┘
│ │
│ 1. Create Payment Request │
│─────────────────────────────────────────────>│
│ │
│ ┌────▼────┐
│ │ Validate│
│ │ Request │
│ └────┬────┘
│ │
│ ┌────▼────┐
│ │ Save │
│ │ to │
│ │ DB │
│ └────┬────┘
│ │
│ 2. Payment Created (ID, URL) │
│<─────────────────────────────────────────────│
│ │
│ ┌────▼────┐
│ │ Create │
│ │ TX │
│ └────┬────┘
│ │
│ ┌────▼────┐
│ │ Submit │
│ │ to │
│ │ Chain │
│ └────┬────┘
│ │
│ 3. Transaction Submitted │
│<─────────────────────────────────────────────│
│ │
│ ┌────▼────┐
│ │ Wait │
│ │ for │
│ │Confirms │
│ └────┬────┘
│ │
│ 4. Payment Confirmed │
│<─────────────────────────────────────────────│
│ │Smart Contract Architecture
B402Payment Contract
Main payment processing contract.
contract B402Payment {
// State variables
mapping(bytes32 => Payment) public payments;
mapping(address => uint256) public balances;
// Structs
struct Payment {
address payer;
address recipient;
uint256 amount;
address token;
PaymentStatus status;
uint256 createdAt;
}
// Functions
function createPayment(...) external returns (bytes32);
function pay(bytes32 paymentId) external payable;
function release(bytes32 paymentId) external;
function refund(bytes32 paymentId) external;
}Escrow Contract
Handles escrow and milestone-based payments.
contract B402Escrow {
struct Escrow {
address payer;
address recipient;
uint256 totalAmount;
Milestone[] milestones;
EscrowStatus status;
}
struct Milestone {
uint256 amount;
bool released;
string description;
}
function createEscrow(...) external returns (bytes32);
function releaseMilestone(...) external;
function dispute(...) external;
}Security Architecture
Authentication
API Keys: For server-to-server communication
JWT Tokens: For user sessions
Wallet Signatures: For blockchain operations
Authorization
Role-based access control (RBAC)
Resource-level permissions
Rate limiting per API key
Data Protection
Encryption at rest (AES-256)
Encryption in transit (TLS 1.3)
Secure key management (AWS KMS / HashiCorp Vault)
Smart Contract Security
Multi-signature wallets for admin functions
Time-locked upgrades
Emergency pause mechanism
Audited by third-party security firms
Scalability
Horizontal Scaling
Stateless API servers
Load balancing across multiple instances
Database read replicas
Redis cluster for caching
Performance Optimization
Connection pooling
Query optimization and indexing
CDN for static assets
Lazy loading and pagination
Monitoring
Real-time metrics (Prometheus)
Log aggregation (ELK Stack)
Error tracking (Sentry)
Uptime monitoring (Pingdom)
Network Architecture
BNB Chain Integration
Mainnet:
Chain ID: 56
RPC: https://bsc-dataseed.binance.org/
Block time: ~3 seconds
Confirmations required: 12
Testnet:
Chain ID: 97
RPC: https://data-seed-prebsc-1-s1.binance.org:8545/
Block time: ~3 seconds
Confirmations required: 6
Node Infrastructure
Multiple RPC endpoints for redundancy
Fallback nodes for high availability
WebSocket connections for real-time events
Archive nodes for historical data
Deployment Architecture
Production Environment
┌─────────────────────────────────────────────────────────────┐
│ Load Balancer (AWS ALB) │
└─────────────────────────────────────────────────────────────┘
│
┌─────────────────────┼─────────────────────┐
▼ ▼ ▼
┌───────────────┐ ┌───────────────┐ ┌───────────────┐
│ API Server │ │ API Server │ │ API Server │
│ (ECS Task) │ │ (ECS Task) │ │ (ECS Task) │
└───────────────┘ └───────────────┘ └───────────────┘
│ │ │
└─────────────────────┼─────────────────────┘
▼
┌─────────────────────────────────────────────────────────────┐
│ RDS PostgreSQL (Multi-AZ) │
└─────────────────────────────────────────────────────────────┘
│
▼
┌─────────────────────────────────────────────────────────────┐
│ ElastiCache Redis (Cluster) │
└─────────────────────────────────────────────────────────────┘Infrastructure as Code
Terraform: Infrastructure provisioning
Docker: Containerization
Kubernetes/ECS: Container orchestration
GitHub Actions: CI/CD pipeline
Monitoring & Observability
Metrics
Request rate and latency
Error rates by endpoint
Payment success/failure rates
Blockchain transaction status
Database query performance
Logging
Structured JSON logs
Centralized log aggregation
Log retention policies
Search and analysis capabilities
Alerting
PagerDuty integration
Slack notifications
Email alerts
Escalation policies
Disaster Recovery
Backup Strategy
Database: Daily automated backups with 30-day retention
Configuration: Version controlled in Git
Secrets: Encrypted backups in secure storage
Recovery Procedures
RTO (Recovery Time Objective): < 1 hour
RPO (Recovery Point Objective): < 15 minutes
Automated failover for critical services
Regular disaster recovery drills
Future Architecture
As we expand to the full AI Agent Marketplace, the architecture will include:
Agent Registry Service: Manage AI agent profiles and capabilities
Discovery Service: Match agents with service requests
Reputation Service: Track and score agent performance
Task Orchestration: Coordinate complex multi-agent workflows
Architecture designed for scale, security, and reliability
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