09/01/2026 updated
MH
partially available
info: Available evenings and weekends
Full-Stack Engineer - Next.js, Python, LLM Integration, Automation (Remote)
Gyeonggi-do, South Korea
Only remote
B.S. Computer Science, Hankyong National University (2016-2022)Software as a ServiceWeb ScrapingPython (Programming Language)PostgreSQLNode.jsNext.jsSystems IntegrationTypeScriptReact.jsLarge Language ModelsSpring BootFastAPIKubernetesFull Stack DevelopmentCloudflare
I'm Donggeun - a full-stack engineer at a Korean B2B SaaS company, where I build and maintain high-availability (HA) failover solutions for enterprise clients. My day job is software that is not allowed to go down; that standard is what I bring to every project.
What I deliver:
- Production web applications, front to back - Next.js, React, TypeScript, Node.js, Python (FastAPI), Java (Spring), PostgreSQL, deployed on Vercel, Cloudflare or AWS.
- LLM feature integration - chatbots, RAG search over private documents, summarization, classification and extraction pipelines - with cost monitoring, caching and an evaluation set, so quality is measurable rather than anecdotal.
- Workflow and document automation - Python plus OpenAI / Anthropic APIs, n8n, browser automation, scheduled collectors that teams run daily.
- Data crawling and ETL pipelines, REST/GraphQL APIs, database design, Docker and Kubernetes deployment.
- Selected work:
- Designed the SplitBrain-resolution logic for a Multi-node HA cluster.
- Migrated a legacy system to a Spring Boot + React web application.
- OpenJDK security upgrade (11.0.13 to 11.0.27) across Windows and Linux build environments.
- Apache Camel migration (2.25.4 to 3.22.4, 13 new libraries plus a Spring Framework upgrade), keeping mail and SMS features compatible.
- How I work:
- Remote only, from Seoul (UTC+9). I do not take on-site or relocation engagements.
- Scope is written down before code starts. Estimates are hour-based and explained.
- Every delivery includes operations documentation, so your team is not dependent on me.
- Payment terms: 30-50% upfront, remainder on delivery.
- Stack: Python, TypeScript, JavaScript, Java, Next.js, React, Node.js, FastAPI, Spring Boot, PostgreSQL, MySQL, Supabase, OpenAI API, Anthropic API, LangChain, RAG, pgvector, Pinecone, REST API, GraphQL, Web Scraping, ETL, n8n, Playwright, Docker, Kubernetes, AWS, CI/CD (GitHub Actions).
- Working language: English (written and spoken, conversational level). I do not work in German - please post or contact me in English.
Experience
Professional experience0 - 5 years
Freelancer since2022
Languages
EnglishGoodKoreanNative speaker
Project history
Enterprise high-availability failover solution (OSGi / Java 11, Active-Standby and Multi-node architectures). Designed the Multi-node SplitBrain resolution logic, migrated a legacy system to Spring Boot + React, ran an OpenJDK security upgrade (11.0.13 to 11.0.27) on Windows and Linux, and completed an Apache Camel migration (2.25.4 to 3.22.4). Source code is a company asset and is not public; architecture-level discussion is available in a scoping call.
Client and personal project work alongside study and full-time employment. Selected projects: KakaoAsset (github.com/kakao-asset) - stock-portfolio web app; real-time market-data crawling, ElasticSearch processing and hand-written Kubernetes manifests on-premise and on AWS (Spring, React, Python, Docker, Kubernetes). HIGHLIGHTING (github.com/swjungle-highlighting/Back) - full-stack YouTube editor for archived live streams; video-analysis design and tuning, server and database design, Chrome extension and chat viewer (Python, Flask, React, Electron). 24_7 - home-training web app with a pose-estimation model judging exercise posture; posture-judgement logic (React, TensorFlow.js). Earlier delivered client work: an Arduino-based lighting alarm device and Android navigation-bar removal on ODROID-C4.