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Fintech

POS Terminal API

Software Engineer Team LeadDar ICT Co. LTD09/2019 — 04/2021

Key Highlights

  • 30% decrease in API latency
  • 100K+ transactions/day (from 30K)
  • ISO 8583 to JSON protocol bridge
  • 15% revenue increase from new vendors
Node.jsExpressISO 8583CLinuxRedis

POS Terminal API

Overview

Re-architected the core RESTful API serving Point of Sale terminals, achieving dramatic performance improvements and enabling the system to handle over 100,000 transactions per day.

The Challenge

The existing API had critical issues:

  • High latency causing transaction timeouts at POS terminals
  • Unable to scale beyond 30K transactions/day
  • Tight coupling between POS vendors and backend logic
  • No protocol abstraction — each vendor required custom integration

    • Solution

    ISO 8583 Protocol Bridge

    Built a protocol translation layer that converts ISO 8583 (the international standard for financial transaction messaging) to JSON and vice-versa:

  • Vendor-agnostic abstraction layer
  • No modifications needed to existing POS terminal software
  • Support for multiple card networks and payment schemes
  • Configurable field mappings per vendor

    • Performance Optimization

  • Connection pooling and request batching
  • Redis caching for frequently accessed data
  • Database query optimization with proper indexing
  • Horizontal scaling with load balancing

    • Results

  • 30% decrease in latency
  • 100K+ transactions/day capacity (up from 30K)
  • 15% revenue increase from connecting new POS vendors
  • Significant market advantage through vendor flexibility

    • Technical Stack

    Node.js, Express, ISO 8583, C, Redis, MongoDB, Nginx, Linux

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