Platform Architecture

MPPFi is built as a decentralized neobank infrastructure for AI agents, leveraging Solana blockchain for transparent settlement and the Machine Payments Protocol (MPP) for standardized agent-to-merchant payments.

System Design

Core Architecture Principles

1. Blockchain-Native: All transactions settled on Solana with sub-second finality

2. Agent-First: Purpose-built for autonomous AI systems

3. Protocol-Driven: Machine Payments Protocol enables interoperable commerce

4. Cryptographically Secure: HSM-backed key management and on-chain enforcement

5. Transparently Auditable: Every transaction verifiable on public blockchain

System Components

1. Platform Layer

MPPFi API Service

• RESTful API for agent account management

• Payment initiation and tracking

• Policy configuration and enforcement

• Webhook event distribution

• Rate limiting and authentication

Technologies: Node.js, Express, TypeScript

Agent Management Service

• AI agent identity provisioning

• Cryptographic keypair generation

• HSM integration for private key storage

• Hierarchical Deterministic (HD) wallet management

• Agent balance and transaction history

Technologies: Rust, AWS CloudHSM

Policy Enforcement Engine

• Spending limit validation

• Merchant allowlist checking

• Multi-signature coordination

• Time-based restrictions

• On-chain policy deployment

Technologies: Rust, Solana Programs (Anchor framework)

2. Blockchain Layer

Solana Network

• Primary settlement layer

• Supports 65,000 TPS (transactions per second)

• Sub-second finality

• Proof of History (PoH) consensus

• Low transaction fees (~$0.00025 per transaction)

MPPFi Smart Contracts (Solana Programs)

├── Payment Processor Program
│   ├── Direct transfers
│   ├── Batch payments
│   ├── Recurring subscriptions
│   └── Escrow management
│
├── Policy Enforcement Program
│   ├── Spending limit validation
│   ├── Merchant allowlist checks
│   ├── Multi-signature approvals
│   └── Time-based restrictions
│
└── MPP Integration Program
    ├── Merchant discovery
    ├── Payment negotiation
    ├── Service token issuance
    └── Refund processing

Deployment: Solana Mainnet-Beta

3. Payment Protocol Layer

Machine Payments Protocol (MPP)

MPP is an open protocol for standardized machine-to-machine payments:

┌──────────────┐         ┌──────────────┐
│  AI Agent    │         │   Merchant   │
│   (MPPFi)    │         │  (API/SaaS)  │
└──────┬───────┘         └──────┬───────┘
       │                        │
       │  1. Discover Endpoint  │
       │───────────────────────>│
       │                        │
       │  2. Get Pricing/Terms  │
       │<───────────────────────│
       │                        │
       │  3. Sign Payment TX    │
       │───────────────────────>│
       │                        │
       │  4. Blockchain Settlement
       │<══════════════════════>│
       │     (Solana)           │
       │                        │
       │  5. Service Token      │
       │<───────────────────────│
       │                        │

MPP Features:

• Service Discovery: Merchants publish .well-known/mpp-manifest.json

• Dynamic Pricing: Real-time quotations based on parameters

• Atomic Settlement: Payment and service access bundled

• Verifiable Receipts: On-chain proof of payment

• Refund Support: Standardized refund workflows

4. Data Layer

Primary Database (PostgreSQL)

├── Agent accounts
├── API keys
├── Payment records
├── Policy configurations
├── Webhook endpoints
└── Audit logs

Blockchain State (Solana RPC)

├── Agent Solana addresses
├── Transaction signatures
├── Smart contract state
├── Block confirmations
└── Account balances

Cache Layer (Redis)

├── Session management
├── Rate limiting counters
├── Real-time balance cache
├── Webhook delivery queue
└── Idempotency keys

Analytics Database (ClickHouse)

├── Transaction analytics
├── Spending patterns
├── Policy violations
├── System metrics
└── Performance monitoring

Architecture Diagrams

Payment Flow Architecture

┌─────────────────────────────────────────────────────────────────┐
│                        AI Agent                                  │
│  ┌──────────────────────────────────────────────────────────┐  │
│  │  Application Logic  (e.g., trading bot, automation)      │  │
│  └───────────────────────┬──────────────────────────────────┘  │
│                          │                                       │
│                          ▼                                       │
│  ┌──────────────────────────────────────────────────────────┐  │
│  │  MPPFi SDK  (TypeScript / Python / Rust)                 │  │
│  └───────────────────────┬──────────────────────────────────┘  │
└────────────────────────────────────────────────────────────────┘
                           │
                           │ HTTPS/JSON
                           ▼
┌──────────────────────────────────────────────────────────────────┐
│                    MPPFi Platform                                 │
│                                                                   │
│  ┌─────────────────┐  ┌─────────────────┐  ┌────────────────┐  │
│  │   API Gateway   │  │  Auth Service   │  │ Rate Limiter   │  │
│  └────────┬────────┘  └─────────────────┘  └────────────────┘  │
│           │                                                       │
│           ▼                                                       │
│  ┌─────────────────────────────────────────────────────────┐   │
│  │              Payment Service                            │   │
│  │  ┌─────────────────────────────────────────────────┐    │   │
│  │  │  1. Validate payment request                    │    │   │
│  │  │  2. Check policy compliance                     │    │   │
│  │  │  3. Verify agent signature                      │    │   │
│  │  │  4. Construct Solana transaction                │    │   │
│  │  │  5. Submit to blockchain                        │    │   │
│  │  └─────────────────────────────────────────────────┘    │   │
│  └──────────────────────┬──────────────────────────────────┘   │
│                         │                                       │
│                         ▼                                       │
│  ┌──────────────────────────────────────────────────────────┐  │
│  │  Blockchain Integration Layer                           │  │
│  │  ┌──────────┐  ┌──────────┐  ┌──────────┐             │  │
│  │  │ Solana   │  │  SPL     │  │  Smart   │             │  │
│  │  │  RPC     │  │  Token   │  │ Contract │             │  │
│  │  │  Client  │  │ Program  │  │  Calls   │             │  │
│  │  └──────────┘  └──────────┘  └──────────┘             │  │
│  └──────────────────────┬──────────────────────────────────┘  │
└─────────────────────────────────────────────────────────────────┘
                          │
                          │ RPC Calls
                          ▼
┌──────────────────────────────────────────────────────────────────┐
│                    Solana Blockchain                              │
│                                                                   │
│  ┌─────────────────┐  ┌─────────────────┐  ┌────────────────┐  │
│  │   Validators    │  │  Block          │  │  State         │  │
│  │   (Consensus)   │  │  Production     │  │  Storage       │  │
│  └─────────────────┘  └─────────────────┘  └────────────────┘  │
│                                                                   │
│  Transaction Finality: ~400ms                                    │
│  Throughput: 65,000 TPS                                          │
└──────────────────────────────────────────────────────────────────┘

Policy Enforcement Architecture

┌────────────────────────────────────────────┐
│      Policy Configuration (API)            │
└──────────────────┬─────────────────────────┘
                   │
                   ▼
┌────────────────────────────────────────────┐
│    Policy Compilation & Deployment         │
│  ┌──────────────────────────────────────┐ │
│  │  1. Parse policy rules               │ │
│  │  2. Compile to Solana bytecode       │ │
│  │  3. Deploy smart contract            │ │
│  │  4. Link to agent account            │ │
│  └──────────────────────────────────────┘ │
└──────────────────┬─────────────────────────┘
                   │
                   ▼
┌────────────────────────────────────────────┐
│     On-Chain Policy Smart Contract         │
│                                            │
│  State:                                    │
│    - Daily/weekly/monthly spent            │
│    - Merchant allowlist                    │
│    - Multi-sig approvals                   │
│    - Time restrictions                     │
│                                            │
│  Functions:                                │
│    - validate_payment()                    │
│    - check_limits()                        │
│    - require_approval()                    │
│    - record_spend()                        │
└──────────────────┬─────────────────────────┘
                   │
                   ▼
┌────────────────────────────────────────────┐
│      Payment Validation (Pre-Flight)       │
│                                            │
│  Every payment checked against:            │
│    ✓ Amount limits                         │
│    ✓ Merchant allowlist                    │
│    ✓ Velocity limits                       │
│    ✓ Time windows                          │
│    ✓ Multi-sig requirements                │
│    ✓ Balance sufficiency                   │
└────────────────────────────────────────────┘

Security Architecture

Key Management

Hierarchical Deterministic (HD) Wallets

Master Seed (stored in AWS CloudHSM)
    │
    ├─> Organization Account (m/44'/501'/0')
    │       │
    │       ├─> Agent 1 (m/44'/501'/0'/0/0)
    │       ├─> Agent 2 (m/44'/501'/0'/0/1)
    │       └─> Agent N (m/44'/501'/0'/0/n)
    │
    └─> Operational Keys
            ├─> Hot wallet (small balance, low latency)
            └─> Cold storage (large reserves, offline)

Private Key Security:

• Keys never leave HSM boundaries

• FIPS 140-2 Level 3 certified hardware

• Multi-party computation (MPC) for critical operations

• Automated key rotation every 90 days

• Audit logging for all key access

Authentication & Authorization

API Key Authentication

Client Request
    │
    ├─> Verify Bearer token
    │     ├─> Check signature
    │     ├─> Validate expiry
    │     └─> Load permissions
    │
    ├─> Rate limiting check
    │     ├─> Per-key limits
    │     └─> Per-IP limits
    │
    └─> Process request

Agent Identity Verification

Payment Request
    │
    ├─> Extract agent signature
    ├─> Reconstruct signed message
    ├─> Verify signature with agent's public key
    ├─> Check nonce for replay protection
    └─> Validate timestamp (max 60s old)

Scalability & Performance

Horizontal Scaling

API Tier: Stateless Node.js services behind load balancer

• Auto-scaling based on CPU/memory

• Kubernetes orchestration

• Target: 10,000 requests/second per region

Database Tier: PostgreSQL with read replicas

• Primary: Writes

• Replicas: Reads (eventually consistent)

• Connection pooling (PgBouncer)

• Sharding by agent ID for future growth

Cache Tier: Redis cluster

• Session data

• Rate limiting counters

• Real-time balance cache

• Pub/sub for webhook distribution

Blockchain Integration

Solana RPC Endpoint Strategy

┌─────────────────────────────────────┐
│  Load Balancer                      │
└────────┬────────────────────────────┘
         │
         ├─> Primary RPC (QuickNode)
         ├─> Fallback 1 (Alchemy)
         ├─> Fallback 2 (Self-hosted)
         └─> Fallback 3 (Helius)

Performance Targets:

• Payment initiation: <200ms (p95)

• Blockchain confirmation: <1s (p95)

• Webhook delivery: <100ms (p95)

Monitoring & Observability

Metrics Collection

Application Metrics (Prometheus)

- API request rate/latency
- Payment success/failure rate
- Policy validation time
- Webhook delivery success rate
- Database query performance

Blockchain Metrics

- Transaction confirmation time
- Gas fees paid
- Failed transaction rate
- Block production rate
- RPC endpoint latency

Business Metrics (DataDog)

- Active agents
- Daily payment volume
- Revenue (platform fees)
- Policy violation rate
- Customer satisfaction (NPS)

Alerting

Critical Alerts (PagerDuty)

• API 5xx error rate > 1%

• Payment failure rate > 5%

• Database connection pool exhausted

• Blockchain RPC unavailable

• HSM connection failure

Warning Alerts (Slack)

• API latency p95 > 500ms

• Webhook delivery failures > 10%

• Policy violations spike

• Rate limit hits increasing

Disaster Recovery

Backup Strategy

Database Backups

• Continuous WAL archiving to S3

• Daily full snapshots

• Point-in-time recovery (PITR) capability

• Retention: 30 days

Blockchain State

• No backup needed (public blockchain)

• Multiple RPC endpoints for redundancy

• Transaction signatures stored in database

Configuration Backups

• Policy configurations in git

• Infrastructure as Code (Terraform)

• Secrets in AWS Secrets Manager

Recovery Procedures

RTO (Recovery Time Objective): 15 minutes RPO (Recovery Point Objective): 5 minutes

Failover Scenarios:

1. Primary database failure → Promote read replica

2. Solana RPC failure → Switch to backup endpoint

3. Region failure → Route traffic to backup region

4. HSM failure → Failover to backup HSM cluster

Compliance & Audit

Audit Logging

All operations logged immutably:

{
  "timestamp": "2025-01-15T14:30:00Z",
  "event_type": "payment.created",
  "agent_id": "agt_7xK9mN2pQ1",
  "actor": "api_key_abc123",
  "action": "create_payment",
  "resource": "pmt_9xL4mP7qR2",
  "details": {
    "amount": 50.00,
    "currency": "USDC",
    "destination": "GHvFF..."
  },
  "blockchain_proof": {
    "signature": "5JzGW8jvKmF3...",
    "block": 245678901
  },
  "ip_address": "203.0.113.42",
  "user_agent": "mppfi-sdk-ts/1.2.0"
}

Retention: 7 years (regulatory requirement)

Regulatory Compliance

AML/KYC: Agent operators verified during onboarding Data Privacy: GDPR/CCPA compliant data handling Financial Regulations: FinCEN reporting for large transactions Blockchain Transparency: All transactions publicly auditable

Technology Stack

Backend Services

• Language: TypeScript (Node.js), Rust

• Framework: Express, Actix-web

• Database: PostgreSQL 15

• Cache: Redis 7

• Message Queue: AWS SQS

• Search: Elasticsearch

Blockchain

• Network: Solana Mainnet-Beta

• Smart Contracts: Anchor Framework (Rust)

• RPC Providers: QuickNode, Alchemy, Helius

• Wallet: @solana/web3.js

Infrastructure

• Cloud: AWS (primary), GCP (backup)

• Orchestration: Kubernetes (EKS)

• IaC: Terraform

• CI/CD: GitHub Actions

• Monitoring: Prometheus, Grafana, DataDog

Security

• HSM: AWS CloudHSM

• Secrets: AWS Secrets Manager

• WAF: Cloudflare

• DDoS Protection: Cloudflare

• Audit: Vanta

Future Architecture Evolution

Planned Enhancements

Multi-Chain Support (2026 Q2)

• Ethereum L2s (Arbitrum, Optimism)

• Cosmos ecosystem

• Polkadot parachains

Advanced AI Features (2026 Q3)

• Autonomous spending optimization

• Fraud detection with ML models

• Natural language policy configuration

Decentralized Governance (2026 Q4)

• Token-based voting on protocol changes

• Community-driven feature prioritization

• Transparent fee structure updates

Next Steps

• Review Authorization Engine for policy enforcement details

• Explore API Reference for endpoint documentation

• Check Quickstart Guide to start building