Available for opportunities

Hi, I'm Kwang.
I build apps people actually use.

Full-stack developer based in Lake Forest, California. I build mobile apps, web platforms, and desktop tools — with a QA background that means I ship things that actually work. Currently building in React Native, Next.js, TypeScript, and Python.

View my work ↓ GitHub
7+
Projects shipped
2
Live apps
5+
Tech stacks
4
Languages spoken

Work

Things I've built

A mix of mobile apps, web platforms, desktop tools, and APIs — built with real users in mind.

🌿
Live Mobile
Clarity in Calm
Wellness app with an encrypted journal (AES-256-GCM), guided breathing exercises, mood tracking, and streaks. Multilingual — English, Korean, Spanish, Hindi.
React Native Expo TypeScript Web Crypto API
Live App Source
🌙
Live Mobile
Dreami
Sleep tracker with session logging, layered ambient sounds, 5-star wake quality ratings, sleep streaks, monthly calendar view, and a gentle gradual alarm.
React Native Expo JavaScript expo-av
Live App Source
🌐
Desktop
Polyglot Translator
Desktop app translating text into 5 languages with phonetic guides, ambiguity detection, tone/domain selectors, and SQLite-persisted history. Two-pass AI translation for natural output.
Tauri 2 React TypeScript Rust SQLite
Source
📊
Web Full-Stack
Channel Hub
Social media dashboard with Google OAuth, Shopify Admin API integration, and Meta/Instagram OAuth. Pulls shop snapshots and live follower counts in a unified view.
Next.js 15 TypeScript PostgreSQL Drizzle ORM Auth.js
Source
⏱
API / Tool
Multilingual Timing Sync
TypeScript REST API that calculates exact silence buffer needed to keep multilingual video overlays in sync (±80ms). Handles Korean, Spanish, and Hindi character timing via ElevenLabs.
TypeScript Node.js ElevenLabs API Jest
Source
🛒
Web
CloudMart
E-commerce frontend with product listings, shopping cart, admin panel, customer support, user order history, and user profiles. Full React SPA.
React Vite Tailwind CSS React Router
Source
🌦
Backend
Weather App
Python Flask web app with city search, current conditions, and 5-day forecast. Includes response caching to minimize API calls and a responsive mobile-friendly UI.
Python Flask OpenWeatherMap API
Source
🤖
PWA
AI Basics
Installable PWA course app teaching practical AI tool usage — ChatGPT, Claude, Gemini, Perplexity. Has quizzes, progress tracking via localStorage, and works fully offline.
Vanilla JS Service Worker PWA
Source

Freelance

Available for hire

QA testing and full-stack development — I can test your product, build it, or both.

70+
Upwork contracts completed
3+
Years on Upwork
2
Services offered: QA + Dev
QA & Testing
  • ✓ Mobile app testing (iOS & Android)
  • ✓ Web app & SaaS QA
  • ✓ AI feature & beta testing
  • ✓ Games QA
  • ✓ Accessibility & usability testing
  • ✓ Bug reports & test documentation
Development
  • ✓ React Native mobile apps
  • ✓ Next.js & React web apps
  • ✓ Cloudflare Pages & Workers
  • ✓ Python Flask backends
  • ✓ PWAs & offline-capable apps
  • ✓ Desktop apps (Tauri + Rust)
View Upwork Profile

About

Quality-first developer

I'm Kwang Yoon, a full-stack developer based in Lake Forest, California. My background in QA testing gave me something most developers don't have from the start — a deeply ingrained habit of thinking about what breaks, not just what works.

I've built mobile apps deployed to production, full-stack web platforms with third-party OAuth, a cross-platform desktop app in Tauri/Rust, Python backends, and TypeScript APIs. I build across the whole stack because I care about how the pieces fit together.

Outside of code, I run a multilingual wellness YouTube channel and speak four languages — which is why a lot of my projects have internationalization built in from day one.

🇺🇸 English 🇰🇷 Korean 🇪🇸 Spanish 🇮🇳 Hindi
Languages
JavaScript TypeScript Python Rust (via Tauri)
Frontend & Mobile
React React Native Next.js Expo Tailwind CSS Vite
Backend & Data
Cloudflare Workers Flask Node.js PostgreSQL SQLite Drizzle ORM
Platforms & Tools
Cloudflare Pages Netlify GitHub Auth.js PWA / Service Workers Linux

Contact

Let's work together

Open to freelance projects, collaborations, and new opportunities. I respond fast.

trac3r1885@gmail.com