Payment Gateway Service

Distributed Backend System

Year

2025

Context

Individual Project

Role

Backend Engineer

Java (Spring Boot 3)

PostgreSQL

Apache Kafka

Resilience4j

Docker

JWT

Flyway

View Source Code

Project Overview

A highly resilient backend orchestration service simulating core banking transaction flows with asynchronous event publishing.

The Problem

Distributed financial systems must handle sudden failures gracefully without dropping transactions or locking up core banking aggregators.

The Solution

I built a fault-tolerant architecture utilizing Apache Kafka for asynchronous messaging and implemented circuit breaker patterns via Resilience4j to prevent cascading system failures.

The Impact & Learning

Achieved 98% instruction coverage via JaCoCo. I learned rigorous enterprise-grade testing discipline and how to design distributed systems built for resilience rather than just functionality.