Hi, I'm Kongsun.

Software engineer

Passionate about building scalable and maintainable systems.

Open to new opportunities · Melbourne or remote

Skills

Programming

Java JavaScript TypeScript Python Kotlin Dart C# Bash SQL C/C++

Frameworks & Libraries

Spring Boot Next.js React.js Node.js React Native Flutter Nest.js .NET Django Tailwind CSS

Cloud & Databases

Azure AWS (EC2, RDS) PostgreSQL Oracle MS SQL Redis

Tools & Technologies

GIT Linux Docker Kafka Jenkins (GitLab CI/CD) VS Code IntelliJ IDEA Postman Codex Claude PicoClaw

Methodologies

Agile Scrum Object-Oriented Programming CI/CD DevOps RESTful API SOAP API Time management

Experience

PiPay

Back-end Engineer · Fintech & Payment Systems

2022 – 2025 +

JavaSpring BootPostgreSQLREST · SOAPGitLab CI/CDScrum Master

Led a team of 5+ engineers to develop a fintech service using Java and Spring boot framework, Postgresql, and Oracle DB, processing $3M in transacitons monthly.
Containerized legacy application stack using Docker, replacing error-prone manual deployments with a consistent, repeatable release process.
Integrated 6+ payment channels including Alipay, UnionPay, Bakong National Payment System, SmartVista, telecom top-up, and internal bill payment systems into a unified platform.
Boosted reliability and performance of a 50,000+ daily transaction pipeline via Redis caching, query optimization, and code profiling, eliminating duplicates, and sustaining 99.9% uptime.

VTECH CO., LTD

Full-Stack Engineer · Mobile & Web Development

2021 – 2022 +

React.jsNext.jsNestJSPostgreSQLTailwind CSS

Engineered responsive admin panels and web platforms for user management and internal operations using Next.js, Ant Design, and Tailwind CSS.
Developed an automated web scraping bot with Puppeteer and Node.js, eliminating manual data collection workflows.
Managed application deployments on AWS EC2 and bare-metal servers via PM2, and owned end-to-end mobile release pipelines for both Google Play and Apple App Store.
Led full-cycle software development projects, from planning and design through development, testing, deployment, and maintenance.

Viettel Cambodia

Software Developer · Java Back-end

2019 – 2021 +

JavaSpring BootDropWizardOracle DB

Maintained a Java-based fintech e-money platform (Spring Boot & Dropwizard) serving 100,000+ daily users, ensuring high availability and consistent payment system performance.
Expanded fintech platform capabilities by implemented new features and third-party integrations for bill payment and mobile airtime top-up services.
Guided external partners through API integration as a provider, managed new partner onboarding configurations, and administered on-premise server deployments.
Developed and maintained mobile applications across React Native, Flutter, and Android native stacks, contributing to both new feature development and ongoing production app maintenance.