# Sanghun Kong — complete portfolio text
Source: https://portfolio.simonkong.me/
Resume PDF: https://portfolio.simonkong.me/resume.pdf
LinkedIn: https://www.linkedin.com/in/sanghunkong/
GitHub: https://github.com/boipqiod

## Sanghun Kong | Portfolio
Source: https://portfolio.simonkong.me/

Sanghun Kong
Full-Stack Software Engineer
Brisbane, Australia Available for new roles
I’m a full-stack engineer with 4+ years of experience building mobile, web, and backend products, backed by 1.5 years in QA. I enjoy taking ideas from early discussions all the way to production—pairing solid architecture with thoughtful UI/UX, and using AI-agent workflows to build and iterate faster.
Tech stack
Frontend
React TypeScript Next.js TanStack Query JavaScript
Backend
Node.js Spring Boot Java Express REST APIs
Mobile
React Native Expo Expo Modules Swift
Data & Infra
PostgreSQL DynamoDB Redis SQL Docker AWS
Quality & Tools
Jest JUnit Fastlane Git Playwright
Explore
Story & Mindset
About me
How I think, habits from my QA days, and what makes building software exciting.
(https://portfolio.simonkong.me/about)
Career History
Experience
Roles, production systems, and engineering ownership across 3 companies since 2020.
(https://portfolio.simonkong.me/experience)
Featured Work
Projects
Software I’ve built and shipped—from commercial payment platforms to independently released iOS apps.
(https://portfolio.simonkong.me/projects)
Writing
Blog
Personal thoughts and notes on building software, side projects, and everything in between.
(https://blog.simonkong.me)
Contact
Let’s talk.
I’m always open to discussing new opportunities, product ideas, or just chatting about tech.
simon.kong.dev@gmail.com LinkedIn (https://www.linkedin.com/in/sanghunkong/)
GitHub (https://github.com/boipqiod)
X (https://x.com/SimonKong__)
Blog (https://blog.simonkong.me)

## Sanghun Kong | About
Source: https://portfolio.simonkong.me/about

Home (https://portfolio.simonkong.me/)
About
Hey, I'm Sanghun Kong. I'm a full-stack software engineer originally from South Korea, now based in Brisbane.
If my name is a bit tricky to pronounce, feel free to just call me Simon!
What I enjoy most is turning ideas into real software that people can actually use—whether that's a complex backend flow or a crisp landing page, I find both just as rewarding.
Before writing code full-time, I spent time working in QA, which left me with a bit of a habit—almost an obsession. Whenever I think "how do I build this?", the immediate next questions are: "what bizarre ways will users find to break this?" and "where is this going to cause trouble down the road?" Even when I'm just working through a routine ticket, I catch myself looking at the entire system flow and how a real human will actually experience it.
My love for making things goes back a long way. When I was a kid, I wanted to be a comic artist, despite being honestly pretty terrible at drawing. Then a friend introduced me to RPG Maker. Writing dialogue, scripting events, and turning my imagination into something interactive completely hooked me. Even if I hadn't become a software engineer, I know I'd still be making things like that today.
That creative itch never really went away. These days, with better tools and AI, the feedback loop between having an idea and bringing it to life is shorter than ever, making building things more fun than it's ever been. I still hold onto the dream of shipping a proper indie game someday.
If you're tinkering with a fun side project, want to chat about games and tech, or just want to build cool software together, feel free to reach out!

## Sanghun Kong | Experience
Source: https://portfolio.simonkong.me/experience

Home (https://portfolio.simonkong.me/)
Experience
EXIMBAY
Full-Stack Software Engineer
Cross-border payments
October 2023 – June 2026 · South Korea
Worked across mobile, web, and backend systems in a team of 1–2 developers. Supported EXIMPay+ (~30,000 MAU) while building and launching 2 new payment products, PG-ON and EXIMLink, using React Native, React, Node.js, and Spring Boot.
- Migrated EXIMPay+’s separate native apps to React Native with zero downtime. Kept existing App Store identities for seamless updates, and rebuilt native integrations as Expo Modules.
- Modernised the EXIMPay+ backend using Spring Boot. Designed a domain-based layered architecture, structuring core payment logic and state transitions into clean entities.
- Strengthened security across mobile and backend systems. Implemented 6 mobile runtime checks based on OWASP guidance, and added MFA and strict session controls for admin and merchant accounts.
- Cut iOS and Android build-and-upload time from about 90 minutes to under 30 minutes. Automated environment-specific builds and uploads to TestFlight and Google Play with Fastlane.
- Built and launched EXIMLink to replace an outdated email-billing system. Delivered an end-to-end payment-link platform featuring merchant invoicing, public REST APIs, and automated webhook integration.
- Developed PG-ON to bring web payments to existing payment terminals. Built a web application allowing merchants to process card and QR payments on existing hardware via a WebView bridge.
- Introduced an AI-assisted development workflow with the team. Structured step-by-step reviews across planning, implementation, and testing, delivering features faster while maintaining high code quality.
Detion
Web & iOS Developer
Mobile identity startup
October 2021 – July 2023 · South Korea
Developed and maintained the DM Plus back office and public APIs, then moved into iOS development. Took over an existing iOS product and launched AIVI. Worked mainly with Express, React, and Swift.
- Removed repeated 5-second polling using Server-Sent Events (SSE). Reduced unnecessary server traffic, allowing the web page to respond immediately once the mobile flow completed.
- Built browser-based face matching and liveness checks. Implemented real-time facial tracking and expression analysis to verify user identity directly in the browser.
- Replaced a paid OCR service with an on-device iOS passport scanner. Built a native module with ML Kit, implementing custom MRZ parsing and check-digit validation.
- Launched AIVI, an AI image generation app for iOS. Implemented photo preprocessing, asynchronous image generation, and local image caching.
NGLE
QA Analyst
Software QA
May 2020 – October 2021 · South Korea
Performed QA for several client projects. Designed test cases from requirements, checked user flows, and reported defects.
- Turned product specifications into structured test cases. Covered expected behaviours, edge cases, and regression scenarios across multiple client projects.
- Identified flow inconsistencies and reproduced defects across user journeys. Documented precise conditions and reproduction steps to help developers investigate and resolve issues.
Education
Bachelor of Computer Science
Yong In University · Graduated February 2021

## Sanghun Kong | Projects
Source: https://portfolio.simonkong.me/projects

Home (https://portfolio.simonkong.me/)
Projects
Professional
EXIMPay+
Official site (https://www.eximbay.com/service/service-eximpayplus-intro.do?lang=EN)
App Store (https://apps.apple.com/app/eximpay/id1501470007)
Google Play (https://play.google.com/store/apps/details?id=com.chainrefund.dmplus)
A mobile app for identity verification, payments, and tax refunds for international customers in South Korea.
My contribution
As the sole mobile engineer, I migrated the iOS and Android apps to React Native. I also developed merchant portal features, payment gateway flows, and backend services.
React Native TypeScript Swift Kotlin Next.js Spring Boot
EXIMLink
Official site (https://www.eximbay.com/service/service-eximlink-intro.do?lang=EN)
A payment-link service where merchants create invoices, send checkout links, and track delivery and payment results.
My contribution
I owned the React frontend and developed Spring Boot features for invoicing, payments, partner APIs, and webhooks, working alongside a backend engineer.
React TypeScript Spring Boot PostgreSQL Storybook
PG-ON
Official site (https://www.eximbay.com/service/service-pg-on.do?lang=EN)
A payment app that enables online card and digital-wallet payments on existing Android terminals.
My contribution
Working with an Android engineer, I built the React web app, Spring Boot APIs, DynamoDB data model, and JavaScript interface to the terminal’s native features.
React TypeScript Spring Boot DynamoDB Android WebView
AIVI
A previously released iOS app for asynchronous AI image generation and editing, with notifications, purchases, and advertising.
My contribution
I took over the existing Swift codebase, completed the main product and third-party integrations, and released the app.
Swift Push Notifications In-App Purchases
View earlier project (1)
Independent
Ulty
Website (https://ulty.me)
App Store (https://apps.apple.com/au/app/ulty-shift-calendar/id6756371021)
An iPhone calendar for creating and managing repeating shift schedules.
My contribution
I independently designed, developed, and released the app, including its local data model and iOS home-screen widget.
React Native Expo TypeScript SQLite Zustand WidgetKit
30:30
Website (https://thirtythirty.simonkong.me)
App Store (https://apps.apple.com/au/app/30-30-app-limits-breaks/id6826460611)
An iPhone app that locks selected apps after 30 minutes of use, then unlocks them after a 30-minute break.
My contribution
I independently designed, developed, and released the app on Apple’s Screen Time APIs, including a usage-monitor extension, custom block screen, and home-screen widget, in four languages.
Swift SwiftUI FamilyControls DeviceActivity ManagedSettings WidgetKit