Jaemin Ko
Frontend Developer
I'm a frontend developer with 3 years of experience who understands problems from the user's perspective and turns business requirements into stable products. I've built experience across diverse environments—from global B2B SaaS booking and website builders to AI content web and kiosk clients, and I've run the kiosks I built at 65-70 offline events in Korea and abroad. Beyond core feature development, I've worked on performance optimization, internationalization, legacy modernization, and Electron application development with integrations for payment modules, printers, and other external systems. I don't stop at implementing features to spec—I consider the user journey and operational environments together. I balance usability, maintainability, and operational stability, collaborating with planning, design, backend, QA, and operations to propose better technical solutions. I aim to be a frontend developer who raises both product quality and team development efficiency by balancing user needs, business goals, and technology.
Experience
Millennial Works Frontend Developer · Kiosk Client
Aug 2025 - Present - Migrated the C# WPF kiosk client to Electron + Next.js (IPC, logging, device auth, JSON per-store settings)
- Built kiosk content (AI photo, tarot, kuji, claw machine, AI music, voice LLM chat) for 65-70 events
- Rolled out the renewed kiosk to ~150 devices: 30K card payments, 8K coupon uses a year (peak 2,000+/day)
- Added WatchDog, kiosk mode, auto shutdown; on-site "app closed" calls stopped
- Set up Sentry monitoring with Slack alerts to catch failures like AI polling fast
- Integrated KICC payments (incl. refunds) and photo, card, and POS receipt printers
- Supported 5 languages and locale-aware date/time formats with next-intl and dayjs
- Built accessible kiosks with Windows TTS and Electron dual screens
- Customized an open-source remote management client and built a kiosk back-office
- Swapped a paid AI music API for open-source ACE-STEP 1.5 Turbo ($0 per request)
- Evaluated Hugging Face models (Z-Image, Qwen-Image, FLUX, WAN, etc.) on a local GPU
CloudHospital Frontend Developer · SaaS Projects
Mar 2023 - Dec 2024 - Built a website builder SaaS (page, header and footer editors with renderer, useFieldArray forms)
- Owned the global hospital booking system (booking/refunds; ~50 to 1,000+ clients)
- Migrated Redux → SWR and Formik → React-Hook-Form; split 1,000+ line components
- Cut First Load JS by ~46% (289kB → 155kB) with dynamic import and tree shaking
- Moved CSR pages to SSR/SSG, parallelized API calls; HTML load -33% (1.79s → 1.2s)
- Applied On-Demand Revalidation and fixed sitemap generation (~5% missing pages recovered)
- Supported 40+ languages and RTL via CSS Logical Properties; GPTs translation automation
- Traced next-auth session leaks to a shared axios instance; added an ESLint guard
Skills
Front-End HTML/CSS, JavaScript, TypeScript, React, Next.js, Electron, Styled-Components, Tailwind CSS, Context API, Zustand, Recoil, React-Query, SWR, OpenAPI Generator, Orval, React-Native, Flutter
Deploy AWS, Vercel
Etc Figma, Postman, Slack, Notion, Git
Side Projects
ZZANGPICK (ZZNPK) Feb 2025 - Present
Frontend Developer
Overview
A community platform for creating and sharing ideal-type world cup games. The Next.js web service is wrapped in React Native WebView to serve web and app from a single codebase.
What I Did
- Split rendering per page with SSR, SSG, ISR, and on-demand revalidation; streaming UI for SSR pages
Next.js, TypeScript, Tailwind CSS, Orval, TanStack Query, Zustand, Motion, GitHub Actions, Vercel, React Native (Expo), NextAuth, Storybook
Pickitoki Jan 2025 - Feb 2025
Frontend Developer
Overview
A walkie-talkie concept diary exchange platform that helps maintain relationships with friends. Completed from planning to deployment in 8 weeks (4 weeks planning, 4 weeks development) as a DND 12th term project with 2 frontend, 2 backend, and 2 designers.
Next.js, TypeScript, Tailwind CSS, Zustand, Motion, Orval, TanStack Query, Serwist (PWA)
Story of Dreams Dec 2024 - Jan 2025
Frontend Developer
Overview
An interactive visual novel using Flutter Flame and Stable Diffusion. Building on Flame prototypes since 2023, separated story/assets from code for easier expansion, and deployed on Google Play.
What I Did
- Added localization after launch; maintaining it with ProGuard, Upgrader, and targetSdk 36
Flutter, Flutter Flame, Stable Diffusion, Shared Preferences
Interactive Portfolio Sep 2022 - Jan 2023 (AI chatbot 2024)
Frontend Developer
Overview
A personal portfolio that boosts engagement with interactive elements. Implemented a LangChain AI chatbot via AWS Lambda in a static CloudFront deployment.
Next.js, TypeScript, Framer Motion, Styled-Components, Recoil, Supabase, LangChainJS, AWS Lambda
Awards
Education
Hansei University B.S. in Computer Science
Feb 2017 - Feb 2023 GPA 4.22/4.5
Major GPA 4.26/4.5
Military Service
Honorably Discharged (Sergeant)
Jan 2018 - Sep 2019