Overview

The Payment Processing Service is the core orchestrator for all payment operations. It handles the complete payment lifecycle from initiation through completion, coordinating with payment gateways and managing transaction state.

Key Responsibilities

Payment Processing

• Validate payment requests and customer data
• Coordinate with Payment Gateway Service for authorization
• Manage payment state transitions
• Handle payment retries and failures
• Emit payment events for downstream systems

Refund Management

• Process full and partial refunds
• Validate refund eligibility
• Track refund status
• Update transaction history

Transaction Orchestration

• Coordinate multi-step payment flows
• Handle async payment responses
• Manage payment timeouts
• Ensure idempotency for payment operations

Technical Details

Technology Stack:

• Runtime: Node.js 20
• Framework: NestJS
• Database: PostgreSQL (transaction records)
• Cache: Redis (idempotency keys)
• Message Broker: Apache Kafka

SLA:

• Availability: 99.99%
• Response Time: < 500ms (p95)
• Transaction Throughput: 1000 TPS

Integration Points

• Payment Gateway Service: Delegates actual payment processing
• Ledger Service: Sends payment events for accounting
• Invoice Service: Receives invoice payment commands
• Fraud Detection Service: Validates transactions (future)