Joonhwan Jeon

Sole developer for KoreHalal, a travel service for Muslim travelers (~3,500 active installs, mainly Singapore, Malaysia, Indonesia and Korea). The team went from frontend + backend + designer to one developer + one designer, and I took over the backend to own the whole stack.

• Mobile app (Flutter): took over a legacy app, then led a full rebuild in 2025 into a 13-domain layered architecture with Riverpod + Freezed; PayPal payments, social login, halal barcode-scanner OCR, real-time 1:1 chat, 5 languages incl. Arabic RTL
• Admin / partner console (Flutter Web) with a three-role permission system
• User web app (React 19, TypeScript, Zustand, Tailwind CSS 4)
• Backend (Laravel 10 on AWS Lambda via Vapor, Aurora MySQL, DynamoDB, SQS, S3/CloudFront): recommendation engine, presigned-upload image server, chat domain
• Internal sales tooling: overseas travel-agency discovery pipeline across 20 countries, quote builder with PDF output, segmented push campaigns

An AI-for-intellectual-property startup. I built the mobile apps for its trademark search and attorney-matching products.

• MarkView — AI image & text trademark search. Led the Swift → Flutter migration (MVVM, Provider, go_router), improved image search performance by 50%, shown at CES 2023
• MarkTong — patent-attorney matching iOS app (Swift, UIKit, Firebase), real-time 1:1 chat with MessageKit, identity verification; released on the App Store

Puts Korean elected officials' campaign pledges next to their public record: bills, votes, attendance and asset disclosures. Python pipelines collect official government data and PDFs, an LLM pipeline extracts 21k+ pledges, and pledge fulfillment is judged by published rules with server-side checks against the model's cited evidence.

• Next.js 16
• Supabase
• Python
• LLM
• Vercel

An offline-first map archive. Drift (SQLite) is the primary store with Supabase as an optional sync layer; Google My Maps KML import, offline tile caching, and supercluster clustering that renders up to 2,800 markers on one map.

• Flutter
• Drift
• Supabase
• flutter_map

Leave photos and notes at real places for others to open nearby. Background geofencing designed around iOS's 20-region limit, journeys rebuilt from photo EXIF GPS, PostGIS spatial queries, and Gemini-generated travel badges and recaps.

• Flutter
• Supabase
• PostGIS
• Geofencing
• Gemini

A shared calendar for couples and families. Share a booking confirmation message and a Supabase Edge Function uses Gemini structured output to pre-fill the event; home-screen widgets and invite links via App Links / Universal Links.

• Flutter
• Supabase
• Gemini
• home_widget

Random trip courses you can actually reach: a filter-then-draw engine over distance ranges per transport mode, subway line and transfer-station normalization, plus roulette / ladder / card-draw game UI and a couple mode.

• Flutter
• Riverpod
• Neon
• Next.js (site)

A mood diary that records each day as a color, in 5 languages with home widgets. Its marketing runs on a multi-agent pipeline built with the Claude Agent SDK, publishing to Threads and Instagram via Supabase pg_cron.

• Flutter
• Supabase
• Firebase
• Claude Agent SDK

The pnpm monorepo behind the app sites above: Vite and Next.js apps merged into one Firebase Hosting site, sitemaps / rewrites / Remote Config generated from a single config file, and GitHub Actions with lint, typecheck, PR preview channels and post-deploy smoke checks.

• pnpm workspaces
• Vite
• Next.js
• Firebase Hosting
• GitHub Actions

A marketplace for local classes and small-group meetups. I co-develop the app in a two-person shared codebase and build the web client solo.

• Flutter
• Riverpod
• Supabase
• Next.js 16