Mobile Money ↔ Stellar Bridge

A backend service that bridges African mobile money providers (MTN MoMo, Airtel Money, Orange Money) with the Stellar blockchain network — enabling low-cost cross-border payments and remittances across Africa and beyond.

🌟 The Problem

Sending money across African borders is expensive and slow. Traditional remittance services charge 7–10% in fees and take hours to days. Meanwhile, 500+ million people across Africa already use mobile money for everyday transactions — but mobile money stops at the border.

💡 The Solution

This platform connects mobile money wallets to the Stellar blockchain, allowing users to:

1. Deposit mobile money (XAF) → receive Stellar tokens (XLM, USDC)
2. Transfer tokens across Stellar's network in ~5 seconds, for fractions of a cent
3. Withdraw Stellar tokens → receive mobile money in the destination country

The sender and recipient interact with their familiar mobile money apps. Stellar handles the cross-border settlement invisibly.

  📱 MTN MoMo (Cameroon)                           📱 Airtel Money (Kenya)
         │                                                  ▲
         ▼                                                  │
  ┌─────────────────────────────────────────────────────────────────┐
  │                    Mobile Money ↔ Stellar Bridge                │
  │                                                                 │
  │   Deposit (XAF → USDC)  ──►  Stellar Network  ──►  Withdraw    │
  │                              (settles in ~5s)                   │
  └─────────────────────────────────────────────────────────────────┘

Use Cases

• Remittances — Send money home across borders at ~1–2% vs 7–10% with traditional services
• Cross-border B2B payments — Pay suppliers in other African countries without expensive wire transfers
• Stable savings — Convert volatile local currency to USDC via mobile money
• Merchant payments — Accept crypto, settle in local mobile money
• Developer integrations — Build payment apps on top of our REST + GraphQL APIs

🚀 Key Features

Core Platform

• Mobile Money Integration — MTN MoMo, Airtel Money, Orange Money with circuit breaker, failover, and batch payouts
• Stellar Blockchain — XLM, USDC, and custom asset support via Stellar SDK + Horizon API
• Dual API — REST (40+ endpoints) and GraphQL (queries, mutations, and real-time subscriptions)
• Real-time Processing — BullMQ job queues with Redis, admin dashboard at /admin/queues
• WebSocket — Live transaction updates with JWT auth, per-user rooms, and Redis pub/sub for horizontal scaling
• Provider Mock Server — Full mock for MTN + Airtel APIs for local development without real credentials

Security & Compliance

• Multi-tier KYC — Tiered identity verification with document upload (S3) and third-party verification (Entrust)
• AML Monitoring — Auto-flagging of suspicious patterns (large transactions, rapid structuring, daily totals)
• Travel Rule Compliance — FATF travel rule data collection for qualifying transactions
• GDPR / Privacy — Data export, deletion, and consent management endpoints
• Sanctions Screening — Automated screening against sanctions lists
• 2FA (TOTP) — Time-based one-time passwords via Speakeasy, required for withdrawals
• RBAC — Role-based access control via Casbin
• Rate Limiting & Audit Logging — Multi-layer rate limiting with full audit trail
• PII Encryption — AES-256-GCM encryption for sensitive data at rest

Financial Engine

• Dynamic Fee Engine — Configurable fee strategies with VIP tiers (25KB+ fee strategy engine)
• Transaction Limits — Provider-specific and KYC-tiered daily limits
• Vault System — Secure fund storage with distributed locking
• Double-Entry Ledger — Internal accounting system with full transaction journal
• Dispute Management — Complete dispute workflow with state machine
• Monthly Statements — Automated PDF statement generation
• Reconciliation — Provider reconciliation workflows

Stellar Protocol (SEP) Support

• SEP-06 — Deposit and Withdrawal API
• SEP-10 — Web Authentication (challenge-response)
• SEP-12 — KYC API (customer CRUD with document upload)
• SEP-24 — Interactive Deposit and Withdrawal (hosted flow)
• SEP-31 — Cross-Border Payments (send-side anchor)

Smart Contracts

• Escrow Contract — Soroban smart contract for escrowed payments (Rust)
• HTLC Contract — Hash Time-Locked Contract for atomic cross-chain swaps (Rust)

Notifications

• Email — SendGrid integration
• SMS — Twilio integration
• Push Notifications — Firebase Cloud Messaging
• WhatsApp — Twilio WhatsApp channel
• PagerDuty — Operational alerting

Developer Tools

• CLI (momo-cli) — Admin tool for auth, status checks, and transaction retries
• Kotlin SDK — Auto-generated from OpenAPI spec
• Postman Collections — Pre-built API collections for testing
• VS Code Extension — Transaction monitor with live WebSocket logs
• Swagger UI — Auto-generated from Zod schemas at /docs (dev mode)

📋 Prerequisites

• Node.js 20+ (LTS)
• PostgreSQL 16+
• Redis 7+
• Docker (optional, recommended for local dev)

🛠️ Quick Start

1. Clone & Install

git clone https://github.com/sublime247/mobile-money.git
cd mobile-money
npm install

2. Configure Environment

cp .env.example .env

Edit .env with your configuration (see .env.example for all ~470 configuration options):

# Database
DATABASE_URL=postgresql://user:password@localhost:5432/mobilemoney

# Redis
REDIS_URL=redis://localhost:6379

# Stellar
STELLAR_NETWORK=testnet  # or 'mainnet'
STELLAR_HORIZON_URL=https://horizon-testnet.stellar.org
STELLAR_ISSUER_SECRET=S...

# Mobile Money Providers
MTN_API_KEY=your_mtn_api_key
AIRTEL_API_KEY=your_airtel_key
ORANGE_API_KEY=your_orange_key

# Security
JWT_SECRET=your_jwt_secret_min_32_chars
SESSION_SECRET=your_session_secret

# Optional: Notifications
SENDGRID_API_KEY=your_sendgrid_key
TWILIO_ACCOUNT_SID=your_twilio_sid

3. Setup Database

npm run migrate:up
npm run seed  # Optional: development data

4. Run

Development (with provider mocks):

npm run docker:dev   # Starts app + Postgres + Redis + provider mock server

Development (standalone):

npm run dev

Production:

npm run build
npm start

Server starts at http://localhost:3000

🧪 Testing

npm test                    # Unit tests (Jest)
npm run test:coverage       # With coverage report
npm run test:watch          # Watch mode
npm run test:e2e            # End-to-end (Playwright)
npm run test:load           # Load testing (k6 / autocannon)
npm run test:mutation       # Mutation testing (Stryker)

Test infrastructure includes:

• Unit & integration tests across controllers, services, middleware, routes
• Pact consumer-driven contract tests for provider APIs
• Playwright end-to-end tests
• k6 load/stress tests with benchmarking against Go vs Node ingest services
• Stryker mutation testing
• Fuzz testing

Coverage reports upload to Codecov on every push to main.

📚 API Documentation

Interactive Docs (Development Only)

Start the dev server and visit:

• Swagger UI: http://localhost:3000/docs
• OpenAPI JSON: http://localhost:3000/docs/openapi.json

The API spec is auto-generated from Zod validation schemas at runtime — no manual YAML to maintain.

Core Endpoints

# Health
GET  /health                          # Liveness probe
GET  /ready                           # Readiness (DB + Redis)
GET  /health/lb                       # Load balancer health

# Transactions
POST /api/transactions/deposit        # Mobile money → Stellar
POST /api/transactions/withdraw       # Stellar → Mobile money
GET  /api/transactions                # List (paginated, filterable)
GET  /api/transactions/:id            # Transaction details
GET  /api/transactions/:id/invoice    # Download completed transaction invoice
POST /api/transactions/:id/cancel     # Cancel pending transaction
POST /api/transactions/:id/dispute    # Open dispute
POST /api/transactions/bulk           # Bulk operations

# Auth
POST /api/auth/register               # Register
POST /api/auth/login                  # Login (returns JWT)
POST /api/auth/2fa/enable             # Enable TOTP 2FA
POST /oauth/token                     # OAuth2 client credentials

# KYC
POST /api/kyc/submit                  # Submit documents
GET  /api/kyc/status                  # Check verification status

# Vaults
POST /api/vaults                      # Create vault
GET  /api/vaults                      # List vaults
POST /api/vaults/:id/transfer         # Deposit/withdraw funds

# Disputes
GET  /api/disputes                    # List disputes
PUT  /api/disputes/:id                # Update dispute status

# Compliance
GET  /api/v1/compliance/travel-rule   # Travel rule data
GET  /api/gdpr/export                 # GDPR data export
DELETE /api/gdpr/delete               # Right to be forgotten

# Stellar SEP Endpoints
POST /sep10/auth                      # SEP-10 authentication
GET  /sep12/customer                  # SEP-12 KYC
POST /sep24/transactions/deposit/interactive  # SEP-24 deposit
POST /sep31/transactions              # SEP-31 cross-border

# Admin
GET  /api/admin/*                     # Admin dashboard endpoints
GET  /api/stats                       # Transaction statistics
GET  /api/reconciliation              # Provider reconciliation
GET  /metrics                         # Prometheus metrics

GraphQL

POST /graphql

Playground: http://localhost:3000/graphql (dev only)

# Query transactions
query {
  transactions(limit: 10) {
    id
    amount
    status
    provider
  }
}

# Create a deposit
mutation {
  createDeposit(input: {
    amount: "10000"
    phoneNumber: "+237670000000"
    provider: MTN
  }) {
    id
    status
  }
}

# Real-time subscription
subscription {
  transactionUpdated(userId: "user-123") {
    id
    status
    updatedAt
  }
}

Authentication

Most endpoints require JWT:

Authorization: Bearer <token>

Admin operations use API key:

X-API-Key: <key>

🔐 Security

Transaction Limits

Type	Limit	Purpose
Minimum	100 XAF	Prevent spam
Maximum	1,000,000 XAF	Fraud prevention

KYC-Based Daily Limits

Level	Daily Limit	Requirements
Unverified	10,000 XAF	Email only
Basic	100,000 XAF	ID + selfie
Full	1,000,000 XAF	Proof of address + video

Provider Limits

Provider	Min	Max
MTN	100 XAF	500,000 XAF
Airtel	100 XAF	1,000,000 XAF
Orange	500 XAF	750,000 XAF

AML Monitoring

Auto-flagging of suspicious transactions:

• Single transaction > 1,000,000 XAF
• 24h total > 5,000,000 XAF
• Rapid structuring (3+ mixed in 15 min)
• Sanctions list screening on every transaction

🏗️ Architecture

Tech Stack

Layer	Technology
API Server	Node.js, TypeScript, Express, Apollo Server (GraphQL)
Database	PostgreSQL 16 (primary + read replicas), Redis 7 (cache, sessions, pub/sub)
Blockchain	Stellar SDK, Horizon API, Soroban smart contracts (Rust)
Job Processing	BullMQ workers, node-cron scheduled jobs
Ingest (High-throughput)	Go service (fasthttp) + Node.js service (Fastify), Redis Streams, NATS JetStream
Security	Helmet, bcrypt, JWT, Speakeasy (TOTP), Casbin (RBAC), AES-256-GCM (PII)
Monitoring	Prometheus, Datadog (dd-trace), Sentry, PagerDuty
Logging	Structured JSON → Loki/Grafana (primary), ELK stack (secondary)
Edge	Cloudflare Workers (.well-known caching)
Infrastructure	Docker, Kubernetes (+ Helm, KEDA), Terraform (AWS)
CI/CD	GitHub Actions (lint, test, build, deploy, rollback)

Project Structure

mobile-money/
├── src/
│   ├── auth/              # Authentication & authorization
│   ├── compliance/        # Travel rule, sanctions
│   ├── config/            # Centralized configuration
│   ├── constants/         # Error codes, enums
│   ├── controllers/       # Request handlers
│   ├── crypto/            # Encryption utilities
│   ├── graphql/           # Schema, resolvers, subscriptions, APQ cache
│   ├── jobs/              # Scheduled & background jobs
│   ├── locales/           # i18n translations
│   ├── middleware/        # Auth, RBAC, rate limiting, audit, error handling
│   ├── models/            # Database models (15 models)
│   ├── openapi/           # Auto-generated API docs (Zod → OpenAPI)
│   ├── queue/             # BullMQ job queue management
│   ├── reports/           # Statement & report generation
│   ├── routes/            # API routes (40+ route files, versioned)
│   ├── services/          # Business logic (58 service files)
│   │   ├── mobilemoney/   # MTN, Airtel, Orange providers + orchestration
│   │   └── stellar/       # Stellar operations, asset management, HSM
│   ├── stellar/           # SEP protocol implementations (6, 10, 12, 24, 31)
│   ├── types/             # TypeScript type definitions
│   ├── utils/             # Helpers & utilities
│   └── websocket/         # WebSocket server (JWT auth, Redis scaling)
├── contracts/             # Soroban smart contracts (Escrow, HTLC)
├── ingest-go/             # High-performance Go callback ingestion
├── ingest-node/           # Node.js baseline for benchmarking
├── workers/               # Cloudflare Workers (edge caching)
├── cli/                   # CLI admin tool (momo-cli)
├── sdk/                   # Auto-generated Kotlin SDK
├── benchmarks/            # k6 load testing suite
├── bridge-starter-node/   # Webhook bridge starter template
├── docs/                  # Extensive documentation (59 docs)
├── docs-portal/           # Docusaurus documentation site
├── extensions/            # VS Code transaction monitor extension
├── postman/               # API testing collections
├── migrations/            # Database migrations (47 migrations)
├── k8s/                   # Kubernetes manifests + Helm chart
├── terraform/             # AWS infrastructure (VPC, ECS, RDS, ElastiCache)
├── elk/                   # ELK stack config (Filebeat, Logstash, Kibana)
├── logging/               # Loki + Grafana + Promtail config
├── scripts/               # Operational scripts (mock server, DB scrub, etc.)
└── tests/                 # Test suites (unit, integration, e2e, pact, fuzz)

🔄 Database

Migrations

47 migration files covering the full schema — transactions (partitioned), users, disputes, vaults, ledger (double-entry), webhooks, KYC, AML alerts, compliance documents, fee strategies, and more.

npm run migrate:create -- migration_name  # Create
npm run migrate:up                        # Run all pending
npm run migrate:down                      # Rollback last
npm run migrate:status                    # Check status

Read Replica Routing

HTTP method-based routing: GET/HEAD/OPTIONS → read replicas (round-robin), write operations → primary. Automatic fallback to primary if replicas are unavailable.

📊 Monitoring & Observability

Metrics

Prometheus metrics at /metrics:

• Transaction counts by status and provider
• API response times (histograms)
• Queue depths and job latencies
• Error rates by category
• Provider availability and circuit breaker state

Health Checks

curl http://localhost:3000/health     # Liveness
curl http://localhost:3000/ready      # Readiness (DB + Redis)
curl http://localhost:3000/health/lb  # Load balancer

Logging

Dual logging stack:

• Primary: Structured JSON → Loki → Grafana (included in docker-compose)
• Secondary: Filebeat → Logstash → Elasticsearch → Kibana (ELK stack configs in elk/)

Alerting

• Sentry — Error tracking and exception monitoring
• Datadog — APM tracing (dd-trace)
• PagerDuty — Operational alerts (low liquidity, provider outages)

🚢 Deployment

Docker

# Development (with mocks, hot reload, Grafana)
docker compose up

# Production build
docker build -t mobile-money:latest .
docker run -p 3000:3000 --env-file .env mobile-money:latest

The production Dockerfile uses a multi-stage build targeting < 200MB image size with a non-root user.

Kubernetes

Pre-built manifests in k8s/ include:

• Deployment — 3 replicas, rolling updates, startup/liveness/readiness probes, resource limits
• Worker Deployment — Separate BullMQ worker pods
• KEDA Autoscaling — Scale workers based on queue depth (threshold: 20 jobs, 1–20 replicas)
• HPA — CPU-based horizontal pod autoscaling for the API
• PodDisruptionBudget — Minimum 2 available pods during disruptions
• Helm Chart — Parameterized deployment in k8s/helm/

kubectl apply -f k8s/

Terraform (AWS)

Full AWS infrastructure in terraform/:

• VPC with public/private subnets across multiple AZs
• ECS Fargate for containerized deployment
• RDS PostgreSQL with Multi-AZ (production)
• ElastiCache Redis with failover
• Application Load Balancer

cd terraform
cp terraform.tfvars.example terraform.tfvars
terraform init
terraform plan -var-file=environments/production.tfvars
terraform apply

CI/CD

GitHub Actions pipeline (.github/workflows/ci.yml):

1. Security — npm audit, Snyk vulnerability scanning
2. Test — Lint, Jest (with Postgres + Redis services), Playwright E2E, Codecov upload
3. Build — TypeScript compilation
4. Docker — Build and push image on main branch
5. Deploy — kubectl apply → rollout status → health check → auto-rollback on failure

🐛 Troubleshooting

See TROUBLESHOOTING.md for detailed error codes and solutions.

Common Issues

Database connection fails:

pg_isready -h localhost -p 5432
# Verify DATABASE_URL format

Redis connection fails:

redis-cli ping  # Should return PONG

Stellar transactions fail:

echo $STELLAR_NETWORK  # Should be 'testnet' or 'mainnet'
curl https://horizon-testnet.stellar.org

Provider mock not working:

# Use docker-compose.dev.yml which includes the mock server
docker compose -f docker-compose.dev.yml up

🚨 Error Handling

Standardized error codes organized by category:

• 4000-4099: Validation (HTTP 400)
• 4010-4019: Authentication (HTTP 401)
• 4030-4039: Authorization (HTTP 403)
• 4040-4049: Not Found (HTTP 404)
• 4090-4099: Conflict (HTTP 409)
• 4290-4299: Rate Limit (HTTP 429)
• 5000+: Server Errors (HTTP 500+)

See src/constants/errorCodes.ts for complete reference.

📖 Documentation

Extensive documentation is available in the docs/ directory (59 documents), covering:

• Architecture — System design, Stellar-EVM bridge architecture, ZK balance proofs research
• Features — KYC, RBAC, GraphQL, SSO, transaction filtering, monthly statements, vaults
• Stellar/SEP — SEP-10/12/31 implementation guides, fee bumping, fee strategy engine
• Infrastructure — CI/CD pipeline, Docker dev setup, ELK stack, database backups, distributed locks
• Integrations — Bridge provider guides, Orange integration, Zapier/Make.com webhooks
• Observability — Metrics, slow query logging, PagerDuty, low liquidity alerts

A Docusaurus documentation portal is available in docs-portal/.

🤝 Contributing

We welcome contributions! See CONTRIBUTING.md.

Workflow

1. Fork the repository
2. Create feature branch (git checkout -b feature/amazing-feature)
3. Make changes and run tests (npm test)
4. Commit (git commit -m 'Add amazing feature')
5. Push (git push origin feature/amazing-feature)
6. Open Pull Request

Pre-commit hooks run ESLint, Prettier, TypeScript checks, and tests automatically.

Good First Issues

Check good first issue label.

🗺️ Roadmap

• SEP-38 implementation (Quotes and Price Streams)
• Additional providers (Vodacom, Tigo, M-Pesa)
• Mobile SDKs (iOS, Android)
• Merchant dashboard UI
• Advanced analytics and reporting dashboard
• Multi-currency settlement support
• Additional stablecoin support (USDT, EURC)
• DeFi protocol integrations
• External accounting integrations (QuickBooks, Xero)

📝 License

MIT License — see LICENSE file.

🙏 Acknowledgments

• Stellar Development Foundation
• Mobile money providers (MTN, Airtel, Orange)
• Open source community

📞 Support

• Issues: GitHub Issues
• Discussions: GitHub Discussions
• Docs: Documentation Portal

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