SeungHyun Kim Andy

I have been building web apps, mobile apps, and servers for 16 years. I designed, built, and deployed a KRW 45M B2B SaaS on my own, and I still maintain it today. I also run four services of my own, so I know what happens after a product ships.

Most of my contracts so far came through Wishket, a major Korean IT outsourcing marketplace.

Highlights

• Wishket Top 1% Pro Partner, 10 contracts, rating 5.00 (7 reviews, full marks in every category: expertise, proactiveness, satisfaction, schedule, communication, and warranty support)
• Built a KRW 45M B2B SaaS solo: 31 data models, 236 APIs (147 GraphQL, 89 REST), 80+ screens, 73 test files
• Kept supporting the same service after delivery on a monthly maintenance contract: 385 hours over 6 months (2026.03 ~ 2026.08)
• Top committer on the frontend team of a Kubernetes MLOps admin console (159 screens): 487 of 1,656 commits (fixed-term senior role, 122 days)
• Since 2025, built and run 4 public services of my own: Go and PostgreSQL servers, uptime checks every minute
• Four contracts with the same client since 2024 (three repeat contracts after the first)
• Built and ran a community of 1,000 concurrent users by myself for 11 years

Client Reviews

Implemented every feature they had doubted was even possible, exactly as planned (business automation software, KRW 45M)

Even as an individual developer, understood the goal very well and matched the project brief exactly (Naver DataLab auto-collection tool)

Fast communication, a real grasp of the project, truly the best service mindset (responsive website for a financial service)

Skills and Experience

Core skills

Work history

3 years 10 months employed (B**** 2 years 3 months, M******** 1 year 7 months), 2 years 5 months freelance, 1 year as a startup founder

Selected Projects

B2B SaaS that generates designs automatically

2025.07 ~ PresentWishket contractKRW 45M137 days + maintenanceRating 5.00

The job Build, on my own and from design to operations, a SaaS with the features the client worried might not be feasible: automating everything from data entry to template-based output generation

• One monorepo holding the user web app, the admin web app, and an API for each (React, Vite, TanStack, NestJS, Prisma, GraphQL)
• Built automation from data entry to template-based output generation, plus order and payment flows
• S3 uploads with automatic thumbnails, GitHub Actions CI, blue/green zero-downtime deploys with rollback

Result Delivered 31 data models, 236 APIs, and 80+ screens single-handedly with a 5.00 rating. After delivery, a monthly maintenance contract followed: 385 hours of operations over 6 months

Kubernetes MLOps platform admin console

2024.12 ~ 2025.04Wishket fixed-term (senior)122 daysRemote 4 days a week

The job Join a multi-person team building the frontend of an admin console for an MLOps platform that runs AI training on GPU clusters

• Built GPU node and cluster resource monitoring dashboards and charts with Next.js (App Router) and TypeScript
• Built resource management screens for single and distributed training jobs, workspaces, and the image registry
• Implemented a Monaco-based Kubernetes YAML editor and real-time SSE notifications

Result In a console of 159 screens and 119 shared components, contributed 487 of 1,656 commits, the most of anyone on the team

Four services I run myself

2025.07 ~ PresentPersonalGo, PostgreSQL, React Router, React Native

The job Separately from client work, plan, build, and keep running my own web and mobile services. Servers in Go and PostgreSQL, web in React Router (SSR), apps in React Native (Expo)

• Escape room information service: collects theme information for 136 venues from the official sites of 8 escape room brands, including booking timetables for 87 of them (per-brand adapters, stores only what changed, retries with backoff on failure). 242 Go tests
• Journaling and trading notes service: turns Korean sentences into structured data with AI (Claude API), and an order tool connected to exchange APIs (blocks duplicate orders, treats timeouts as unknown results). Korean, English, and Japanese, 347 Go tests, shipped to iOS TestFlight
• Music sharing service: recommends similar tracks from per-track audio feature vectors, sitemaps split by page type, schema.org structured data
• Operations console: opens every service once a minute as an uptime check, counts search engine and AI crawler visits per bot

Result Running 4 public services alone. Went through the whole operations cycle myself: deploys, incident response, and search visibility

Global cross-border commerce platform

2023.03 ~ 2024.09M******** full-timeNext.js, Nest.js, MySQL

The job Move a live service's old code to a new stack while adding international payments

• Migrated the legacy stack (JavaScript, React, Express) to TypeScript, Next.js, React Query, Emotion, and Nest.js
• Designed and built per-country currency selection, exchange rate updates, and currency conversion
• Integrated card, KRW, and local currency payment APIs
• Built features across the admin console, user client, and server API (MySQL, Sequelize, Docker), with GitHub Actions deploy automation

Two shopping mall API integrations

2026.03 ~ 2026.07Wishket fixed-term, contractSpring, Cloudflare Workers

The job Reliably connect a shopping mall platform's (Cafe24) open API to other systems

• ERP ↔ shopping mall integration backend (Spring, MyBatis, fixed-term): syncing products, options, images, prices, and stock; mapping categories, brands, manufacturers, and carriers; collecting orders, exchanges, and claims and sending tracking numbers; issuing and refreshing OAuth 2.0 tokens
• Multilingual shopping mall review sync service (Cloudflare Workers, Hono, TypeScript, contract): translates reviews and moves them to stores in other languages, retries only transient errors, traces failures through run history, prevents duplicates with review fingerprints. Worked around the API's 100-item query limit with page-by-page queries

Search engine and AI search visibility

2025.07 ~ PresentServices I run myselfSSR, sitemaps, schema.org JSON-LD

The job Make sure my own services are read and understood properly by Google, Naver, and AI search

• Built the web apps with server rendering (React Router SSR) so crawlers can read content without JavaScript
• Split sitemaps by page type (8 across two services), set canonical URLs in one place, and kept pages like login and sign-up out of the index
• Added schema.org structured data (16 JSON-LD types) to tracks, posts, playlists, people, Q&A, and more
• Counted Googlebot, Naver Yeti, and AI crawlers such as GPTBot, ClaudeBot, and PerplexityBot per bot from server access logs, and registered the sites with Naver Search Advisor

Result Applied and now operate the technical work search visibility needs (crawling, indexing, structured data, bot checks) across several services

Education services

2016 ~ 20264 contracts, personalPHP, CodeIgniter, React Router

The job Build education services for instructors, academies, and students, and add features to services already in operation

• Online exam authoring and auto-grading platform (2 Wishket contracts, 2024): added and designed admin features on a live legacy PHP (CodeIgniter) service (AWS, Linux, Nginx, MySQL)
• Social sign-up and password recovery for the same client (Wishket, 2024), and a review demo of an AI survey agent (2026)
• Video lecture LMS platform (personal, 2016): course site and admin web, hybrid app, video streaming (PHP, CodeIgniter, MySQL)

Result Four contracts with the education platform client since 2024. Worked on both the learner screens and the admin features

Other Experience

Wishket partner work 2024.06 ~ Present

• Exam authoring and grading platform: added features to a live legacy PHP (CodeIgniter) service used by instructors, academies, and students (AWS, Linux, Nginx, MySQL)
• Naver DataLab collection tool: DataLab and search ad API integration, daily batch collection into a database, a React trend comparison screen, Docker Compose. Warranty-period support earned a separate rating of 5.00

Other contracts 2026

• Review demo of the AI survey agent "Ddokform" (2026.08): a repeat contract with a client I have worked with since 2024. Built and deployed in one day a demo web app with survey creation and editing, link and QR sharing, response collection with live tallies, report screens, and KakaoTalk and email send previews (React Router, Upstash Redis, Vercel), demo at ddokform.vercel.app
• Multilingual shopping mall review sync service (2026.05 ~ 2026.07): see the shopping mall API integrations above

Freelance (3 freelance clients) 2022.09 ~ 2023.02

• Artist social network platform (a large enterprise's in-house venture): full-stack web, app, and server development for a creator matching service (React, Node.js, TypeScript, MySQL, Flutter, AWS)
• Asset management, real estate, and financial information mobile app: an app of about 100 pages built from one codebase for iOS and Android, with statistics and dashboard screens designed and built (Flutter, Figma, Naver Cloud Platform)

B**** (Frontend Engineer, R&D) 2020.02 ~ 2022.04, 2 years 3 months

Owned the apps, web, API servers, database design, Firebase integration, and deploy automation of services that analyze sensor data with AI, from kickoff to release.

• Early calf disease detection service: designed and built the Flutter app (MVVM), Node.js and TypeScript API server and MySQL schema, CloudWatch usage logs, scrollable graph and data table widgets, farmer alerts on suspected disease
• Posture balance measurement and exercise prescription solution: Flutter app, 5-page prescription report PDF generation, replay with synchronized video and graphs, Firestore schema design
• Video tagging desktop app for AI training data: Electron and React app playing 6 video channels at once alongside sensor signal graphs, plus a usage statistics web app, API, and PostgreSQL schema
• Deep learning experiments on IMU sensor signals: converted signals to images for MobileNet transfer learning (Python, TensorFlow)

Game for children using a BLE sensor device 2020.03

• Unity game development, Android and iOS bridge plugins for BLE sensor data communication

GetWalk (Startup, CTO) 2017.03 ~ 2018.02

Co-founded a location-based pedometer app that rewards walking, with my brother, and handled every part of development.

• Android app (Java, step counting from the accelerometer), Node.js API server, MongoDB location queries, Crontab batches, React admin web, AWS Elastic Beanstalk deploys

Music sharing community (personal) 2011.02 ~ 2022.09

A community I built and ran myself, from the server to the web, for 11 years.

• Handled 1,000 concurrent users: php-apc caching, MySQL master-slave read/write split, DNS round-robin load distribution, Docker to simplify server setup
• Moved from PHP, CodeIgniter, and jQuery through React to Next.js (SSR), TypeScript, and GraphQL; Redis upload queue; Telegram alerts when the server goes down

Other personal projects

• News and trending issues responsive web 2022: Node.js, Express, TypeScript API, React web and admin pages
• Web service collection 2012: real-time chat, a digest of popular community posts, sharing of creative work, photos, and short videos, disposable email addresses, and more
• DuckSync: a desktop app that syncs two directories in real time (Electron, Watchman, rsync)
• Analyzed and fixed issues in libraries I used and contributed pull requests (PR #1, #2, #3, #4)

FlowFly 2017.09

• Unity casual game with random obstacle generation

Brick Factory Tycoon 2016.10

• Unity business simulation game with quest rewards, in-app purchases, and rankings

Ant Millionaire 2016.05

• Unity life simulation game

Unity-native app communication bridge plugin

• A plugin for data communication between Unity and native (Android, iOS) code

Tech Stack

Frontend

• Language: TypeScript, JavaScript(ES6)
• Library: React, Next.js, React Router, Recoil, Redux, MobX, React Query, Apollo Client, Emotion, StyledComponent, Tailwind CSS, Webpack, Babel, ESLint, Prettier, i18n
• Architecture: DDD(Domain-driven design), SSR, SEO, W3C Standards, a11y, Semantic HTML

Backend

• Language: TypeScript, Java, PHP, Go
• Library: Node.js, Nest.js, Express, Hono, JWT, Apollo Server, ORM(Sequelize, TypeORM, Prisma, Mongoose), Spring Boot, MyBatis, CodeIgniter
• Database: MySQL, PostgreSQL, MongoDB
• Architecture: RESTful API, GraphQL, MVC

Mobile

• Language: Dart, Java, Kotlin, C++, Swift
• Library: Flutter, React Native, Expo, Fastlane, Firebase, Android, Retrofit, Glide, Gson, XML Layout, NDK, OpenCV, JCodec, Ionic Framework
• Architecture: MVVM, MVC

DevOps · Infrastructure

• AWS: EC2, S3, RDS, Lambda, CloudWatch, Elastic Beanstalk, Amplify, Route 53, API Gateway, CloudFront, SES
• Firebase (used in production at B****): Firestore, Crashlytics, Realtime Database, Remote Config, Dynamic Links, Authentication, Cloud Messaging
• CI/CD: Github Actions
• ETC: Docker, Cloudflare Workers, Shell Script, pm2, Nginx, DNS Round-robin, Reverse Proxy, Apache, Git

Desktop (macOS · Windows)

• Language: JavaScript, Python
• Library: Electron.js, PyQt

AI · Machine Learning

• LLM: Claude API (Korean sentences → structured data)
• Language: Python
• Library: TensorFlow, Keras, Scikit-learn, NumPy, Matplotlib
• Model: MobileNet V2, SVM, Transfer Learning

Games

• Language: C#
• Library: Unity, Google Play Game Service, Firebase

Other

• ETC: Solidity, Go-Ethereum, Web3.js, OpenCV, WebSocket
• Collaboration: Postman, Slack, Notion, Figma, Jira, Confluence, Asana, Zeplin