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Hi, I’m Yongjae Kim, a product engineer with 4 years of frontend experience in production SaaS. I build full-stack AI products and operate Nativ, a live AI tutor for language learners, with a hybrid RAG pipeline and LLM-as-Judge in production. I'm proficient with React, Next.js, TypeScript, Python, and FastAPI, and I care about accuracy, cost efficiency, and robust CI/CD. I enjoy shipping features end-to-end, writing tests, and designing user-centric interfaces.…Hi, I’m Yongjae Kim, a product engineer with 4 years of frontend experience in production SaaS. I build full-stack AI products and operate Nativ, a live AI tutor for language learners, with a hybrid RAG pipeline and LLM-as-Judge in production. I'm proficient with React, Next.js, TypeScript, Python, and FastAPI, and I care about accuracy, cost efficiency, and robust CI/CD. I enjoy shipping features end-to-end, writing tests, and designing user-centric interfaces.

Yongjae Kim

Full Stack Developer, Front-End Developer, Web Developer

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Hi, I’m Yongjae Kim, a product engineer with 4 years of frontend experience in production SaaS. I build full-stack AI products and operate Nativ, a live AI tutor for language learners, with a hybrid RAG pipeline and LLM-as-Judge in production. I'm proficient with React, Next.js, TypeScript, Python, and FastAPI, and I care about accuracy, cost efficiency, and robust CI/CD. I enjoy shipping features end-to-end, writing tests, and designing user-centric interfaces.…Hi, I’m Yongjae Kim, a product engineer with 4 years of frontend experience in production SaaS. I build full-stack AI products and operate Nativ, a live AI tutor for language learners, with a hybrid RAG pipeline and LLM-as-Judge in production. I'm proficient with React, Next.js, TypeScript, Python, and FastAPI, and I care about accuracy, cost efficiency, and robust CI/CD. I enjoy shipping features end-to-end, writing tests, and designing user-centric interfaces.

Available to hire

Hi, I’m Yongjae Kim, a product engineer with 4 years of frontend experience in production SaaS. I build full-stack AI products and operate Nativ, a live AI tutor for language learners, with a hybrid RAG pipeline and LLM-as-Judge in production.
I’m proficient with React, Next.js, TypeScript, Python, and FastAPI, and I care about accuracy, cost efficiency, and robust CI/CD. I enjoy shipping features end-to-end, writing tests, and designing user-centric interfaces.

Skills

Experience Level

Expert

Expert

Expert

Expert

Expert

Expert

Expert

Expert

Expert

Language

Korean

Fluent

English

Advanced

Work Experience

Frontend Engineer at VNTG

November 1, 2025 - February 1, 2026

Digital transformation platform for manufacturing enterprises. Defined a roadmap to automate frontend code generation from Figma designs and requirements. Built a 4-stage Spec-to-React pipeline (Claude Code sub-agents) with automated quality gates and auto-correction (WCAG AA, semantic HTML), improving HTML quality from 50–70% to 95% and achieving 90%+ Figma-to-React component mapping accuracy.

Frontend Engineer at Bold9 Ltd

February 1, 2026 - Present

SaaS e-commerce fulfilment platform for online sellers. Enhanced core business pages with advanced search, interactive data tables, and inline editing; created a real-time operations dashboard; developed large-scale forms (70+ fields) with dynamic validation to reduce re-renders; built a cross-platform push notification system; introduced automated unit, integration, and visual testing with Vitest and Storybook, increasing test coverage from 10% to 70% and cutting CI runtime by 50% via parallel tests.