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
4
Apps in closed testing — live release mid-July
70+
Freelance contracts
5+
Tech stacks
4
Languages spoken

Work

Things I've built

Four Android apps published to Google Play — wellness, sleep, and productivity tools built with React Native and Expo.

🌙
Play Store 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
🌿
Play Store 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
📓
Play Store Mobile
Clarity Journal
Encrypted wellness app with a private journal, guided breathing, stretch routines, and a Feelings Journal — 48-emotion wheel, tappable prompts, biometric lock, and AES-256-GCM encryption. Android APK built and deployed.
React Native Expo TypeScript expo-secure-store expo-local-authentication
Download APK Source
🧾
Play Store Mobile
Invoicer
Freelancer invoice generator with client management, PDF export, native date pickers, and a lifetime unlock via in-app purchase. Includes a full onboarding flow, free tier enforcement, and a clean dashboard with usage tracking.
React Native Expo SDK 56 TypeScript SQLite NativeWind RevenueCat
Download APK

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