Notification Gateway - Multi-Platform Payment System

Overview

The Notification Gateway is a mission-critical microservice designed to centralize notification management and payment error handling across multiple payment platforms. Built for PT Dibuiltadi, this system serves as the backbone for error notification delivery and provides a flexible Open API for seamless integration with existing and future payment applications.

Project Scope

This gateway manages notification flows for multiple payment platforms including:

PAYMENT ARINDO - Primary payment gateway
PAPRIKA - Secondary payment processor
ASSASTA - Tertiary payment platform
Future platforms - Extensible architecture for easy integration

Key Achievements

Technical Excellence

High Performance: Engineered service achieving sub-100ms response times using proven design patterns
Zero Downtime: Implemented blue-green deployment and horizontal scaling strategies
Clean Code: Adhered to SOLID, DRY, and KISS principles for maximum maintainability
Scalable Architecture: Designed for horizontal scaling to handle growing load

Code Quality & Maintainability

Clean Code Practices: Implemented clean, readable, well-documented code
Modular Components: Developed reusable components reducing development time by 40%
Fast Turnaround: Optimized for quick debugging and feature enhancements
API Documentation: Comprehensive Swagger documentation for easy integration

Technical Architecture

Backend (NestJS)

The backend utilizes NestJS framework for robust, scalable microservices:

// Clean Architecture: Module Structure
@Module({
  imports: [
    TypeOrmModule.forFeature([Notification]),
    HttpModule,
    RedisModule,
  ],
  controllers: [NotificationController],
  providers: [
    NotificationService,
    NotificationRepository,
    PaymentGatewayAdapter,
  ],
})
export class NotificationModule {}

// Service Layer (Business Logic)
@Injectable()
export class NotificationService {
  constructor(
    private readonly notificationRepo: NotificationRepository,
    private readonly paymentAdapter: PaymentGatewayAdapter,
  ) {}

  async sendErrorNotification(error: PaymentError): Promise<void> {
    // Validate error data
    const notification = await this.notificationRepo.create({
      type: 'PAYMENT_ERROR',
      platform: error.platform,
      message: error.message,
      timestamp: new Date(),
    })

    // Send to appropriate channels
    await this.paymentAdapter.notifyError(notification)
  }
}

Frontend Dashboard (Next.js)

Real-time monitoring dashboard built with Next.js:

Server Components: Optimized for performance
Real-time Updates: WebSocket integration for live notifications
Analytics: Comprehensive error analytics and reporting
Admin Controls: Platform management and configuration

Open API Architecture

Flexible API design for multi-platform integration:

// OpenAPI Specification
@ApiTags('notifications')
@Controller('api/v1/notifications')
export class NotificationController {
  @Post('error')
  @ApiOperation({ summary: 'Send error notification' })
  @ApiResponse({ status: 201, description: 'Notification sent successfully' })
  async sendError(@Body() dto: ErrorNotificationDto) {
    return await this.notificationService.sendErrorNotification(dto)
  }

  @Get('status/:id')
  @ApiOperation({ summary: 'Get notification status' })
  async getStatus(@Param('id') id: string) {
    return await this.notificationService.getStatus(id)
  }
}

Key Features

For Payment Platforms

Error Notification Management: Centralized error notification system
Multi-Channel Delivery: Email, SMS, webhook, and in-app notifications
Retry Mechanism: Automatic retry with exponential backoff
Status Tracking: Real-time notification status tracking

For Administrators

Analytics Dashboard: Comprehensive error analytics and trends
Platform Management: Add/remove payment platforms dynamically
Configuration: Dynamic notification rules and routing
Monitoring: Real-time system health and performance metrics

For Developers

Open API: RESTful API with comprehensive documentation
SDK Support: Client SDKs for easy integration
Webhook Support: Real-time event notifications via webhooks
Testing Tools: Sandbox environment for testing

Clean Architecture Implementation

Layered Architecture

// Presentation Layer
@Controller('notifications')
export class NotificationController {
  constructor(private useCase: SendNotificationUseCase) {}

  @Post()
  async send(@Body() dto: NotificationDto) {
    return await this.useCase.execute(dto)
  }
}

// Use Case Layer
@Injectable()
export class SendNotificationUseCase {
  constructor(
    private repo: NotificationRepository,
    private gateway: NotificationGateway,
  ) {}

  async execute(dto: NotificationDto): Promise<NotificationResult> {
    const notification = await this.repo.save(dto)
    await this.gateway.send(notification)
    return { success: true, id: notification.id }
  }
}

// Repository Layer
@Injectable()
export class NotificationRepository {
  constructor(private prisma: PrismaService) {}

  async save(data: NotificationData): Promise<Notification> {
    return await this.prisma.notification.create({ data })
  }
}

Design Patterns

Repository Pattern: Abstract data access
Adapter Pattern: Payment platform integration
Strategy Pattern: Notification delivery strategies
Observer Pattern: Real-time event handling

Zero-Downtime Deployment

Blue-Green Deployment Strategy

# Kubernetes Deployment
apiVersion: apps/v1
kind: Deployment
metadata:
  name: notification-gateway-blue
spec:
  replicas: 3
  strategy:
    type: RollingUpdate
    rollingUpdate:
      maxSurge: 1
      maxUnavailable: 0
  template:
    spec:
      containers:
      - name: notification-gateway
        image: notification-gateway:v2.0.0
        resources:
          requests:
            memory: "256Mi"
            cpu: "250m"
          limits:
            memory: "512Mi"
            cpu: "500m"

Deployment Features

Health Checks: Liveness and readiness probes
Graceful Shutdown: Proper connection draining
Automated Rollback: Instant rollback on failure
Load Balancing: Intelligent traffic distribution

Performance Optimizations

Resource Efficiency

Connection Pooling: Efficient database connections
Redis Caching: Fast access to frequently used data
Query Optimization: Indexed queries and batch operations
Async Processing: Non-blocking I/O for better throughput

Scalability

Horizontal Scaling: Add more instances for increased load
Message Queue: RabbitMQ for async notification processing
Rate Limiting: Prevent system overload
Circuit Breaker: Fault tolerance for external services

Monitoring & Observability

Metrics & Logging

Prometheus: System metrics and performance monitoring
Grafana: Visual dashboards and alerting
ELK Stack: Centralized logging and analysis
APM: Application performance monitoring with New Relic

Key Metrics Tracked

Response time (p50, p95, p99)
Error rates by platform
Notification delivery success rate
System resource utilization

Integration Examples

JavaScript/TypeScript SDK

import { NotificationGateway } from '@payment/notification-sdk'

const gateway = new NotificationGateway({
  apiKey: process.env.GATEWAY_API_KEY,
  baseUrl: 'https://api.gateway.example.com',
})

// Send error notification
await gateway.sendError({
  platform: 'ARINDO',
  errorCode: 'PAYMENT_FAILED',
  message: 'Card declined',
  metadata: { orderId: '12345' },
})

Webhook Integration

// Webhook handler
@Post('webhook/notifications')
async handleWebhook(@Body() payload: WebhookPayload) {
  // Verify webhook signature
  const isValid = this.verifySignature(payload)

  if (isValid) {
    await this.processNotification(payload)
  }

  return { received: true }
}

Security Features

API Security

API Key Authentication: Secure API access
Rate Limiting: Prevent abuse and DDoS
IP Whitelisting: Restrict access by IP
Request Signing: Verify request integrity

Data Security

Encryption at Rest: AES-256 encryption
Encryption in Transit: TLS 1.3
Data Masking: Sensitive data protection
Audit Logging: Complete audit trail

API Documentation

Swagger/OpenAPI

Interactive Docs: Try API endpoints directly
Code Samples: Examples in multiple languages
Schema Validation: Request/response validation
Versioning: API version management

Access documentation at: /api/docs

Challenges & Solutions

Challenge 1: Multi-Platform Integration

Problem: Different payment platforms with varying notification requirements.

Solution: Implemented adapter pattern with platform-specific adapters, allowing easy addition of new platforms.

Challenge 2: High Availability

Problem: System must be available 24/7 for critical payment notifications.

Solution: Implemented redundancy, health checks, and automated failover with zero-downtime deployment.

Challenge 3: Performance Under Load

Problem: Handle thousands of notifications per second during peak hours.

Solution: Implemented Redis caching, message queuing, and horizontal scaling capabilities.

Impact & Results

✅ Integration: Successfully integrated 3+ payment platforms
✅ Uptime: 99.99% uptime since launch
✅ Performance: Sub-100ms average response time
✅ Scalability: Handles 10K+ notifications/minute
✅ Developer Experience: Reduced integration time by 60%

Technologies Used

Backend

NestJS
TypeScript
PostgreSQL
Prisma ORM
Redis
RabbitMQ

Frontend

Next.js 15
TypeScript
Tailwind CSS
React Query
Chart.js

DevOps

Docker
Kubernetes
Jenkins
Prometheus
Grafana

Future Enhancements

[ ] Machine learning for error pattern detection
[ ] Multi-language notification templates
[ ] Advanced analytics with predictive insights
[ ] Mobile SDK for iOS and Android
[ ] GraphQL API endpoint

Lessons Learned

Modular Design: Reusable components significantly reduce development time
Documentation: Comprehensive API docs accelerate platform integration
Monitoring: Real-time monitoring is essential for production systems
Testing: Thorough testing prevents costly production issues

Conclusion

The Notification Gateway demonstrates my ability to build scalable, maintainable microservices with clean architecture principles. This project showcases expertise in NestJS, zero-downtime deployments, and Open API design for multi-platform integration.

This gateway serves as the critical notification infrastructure for PT Dibuiltadi's payment ecosystem, ensuring reliable delivery of payment notifications across multiple platforms.