Jaegyeong Kim
Frontend Engineer
Engineer who digs into problems until they become structure
A frontend engineer with 6 years of experience, I've designed and built 10 React-based services and 3 landing pages for KOKKOK, an O2O platform in Laos, leading a 2–6 person team along the way.
I consolidated separate repos into a monorepo, automated manual deploys with CI/CD, and introduced runtime type validation to cut outages from API drift — trimming the initial bundle by up to 92% and dev server startup by up to 88%, raising the whole team's development speed and stability.
Tech Stack
Core
Platform / DX
Infra
Side
Experience
Key Achievements
View portfolio →Type-safe API Layer
Read article (KR) →Typia runtime validation + pessimistic type design. When the API spec drifts, the service keeps running, and mismatched fields can be pinpointed instantly, cutting debugging time. Generalized via a factory function, now applied automatically across all 10 apps. Splitting the validation dev mode cut dev server startup by up to 88% (53.8s → 6.3s)
Monorepo Architecture
Read article (KR) →Migrated to pnpm workspace + Turborepo. 10 apps share identical packages — 200+ shared code modules · 2,245 tests safeguarding core logic
CI/CD Automation
Read article (KR) →Split the React (SPA) deploy pipeline into build and deploy stages, with a shared validation workflow that checks every deploy automatically. Even inside the monorepo, services deploy independently, deploy and rollback in minutes
Bundle Optimization
Lazy imports · manualChunks · removed 1,600 barrel files. Initial bundle cut up to 92% (4,990kB → 375kB), index.js cut up to 91% (925kB → 86kB)
Global State Optimization
Converted ContextAPI-based global state to Zustand + selectors to minimize re-render scope. useModal over-subscription caused a 401 + white screen bug on logout — fixed, eliminating full Header re-renders (confirmed via React DevTools Profiler). Moved shared code into packages/ and rolled it out across all 10 apps.
Career
Coconutsilo
Frontend Engineer / FE Team Lead
Dec 2020 – Present
KOKKOK, an O2O platform in Laos. Designed, built, and operate 10 React-based services and 3 Next.js landing pages. Leading a 2–6 person FE team since 2021.
- Led timing and direction decisions for TypeScript adoption, monorepo migration, and Vite migration
- Documented local setup, code conventions, architecture, and deploy process — new hires onboard on their own, cutting communication overhead
- Established type naming rules, component patterns, and a pre-PR checklist
Side Projects
Asset Management Studio
Live ↗Solo (planning, design, development, and deployment end-to-end)
May 2026
A full-stack web app unifying 12 asset types — stocks, ETFs, deposits, real estate, crypto, and more. Auto-calculates returns and IRR, integrates live quotes, with Playwright E2E and Vitest unit tests.
Bulletin Viewer PWA (Jamsil Joongang Church)
Live ↗Solo (planning, design, development, and deployment end-to-end)
Jun 2026
A responsive PWA usable across mobile, tablet, and web, running in production for real users. Minimizes image network requests with 3-layer caching — R2 Cache-Control, next/image optimization, and cache-tag-based revalidation. Also built a crawling-based bulk import pipeline. A Flutter-based iOS/Android app is in development and preparing for release.
Education
Samsung SW Academy For Youth (SSAFY, 3rd cohort)
Jan 2020 – Dec 2020
Korea University (Sejong) — Dept. of Control & Instrumentation Engineering
Mar 2013 – Feb 2020