Software Engineer
Seoul, South Korea
📧 stark@hey.com | 🌐 https://kyoungwon.me | GitHub: github.com/leegeng
Impact-driven software engineer with over 10 years of experience building scalable backend systems and product-focused features. Strong foundation in high-traffic distributed services, having led development efforts at both large tech companies and startups. Passionate about creating meaningful user-facing products, from idea to production, with a mindset rooted in business impact and autonomy.
Dec 2019 – Present, Seoul, South Korea
🔍 Recommendation System Enhancement
- Developed and improved similar post/product recommendation systems based on pgvector and Pinecone
- Introduced dual write approach for vector embeddings to handle embedding model transitions
- Implemented category and region-based recommendation logic branching for global environments (Japan, North America)
🛍️ Automated Link Listing Feature Development
- Implemented crawler and automated product registration for secondhand platforms (Mercari/Jmty)
- Built banner settings and region management features through Admin pages for operational efficiency
- Introduced listing reminder push notifications and early access features → contributed to improved user conversion rates
🖼️ Image Center Coordinate Extraction and Thumbnail Automation
- Implemented image center coordinate extraction and square cropping features to improve AI image recommendation quality
- Completed end-to-end pipeline with integrated frontend/backend processing and comprehensive test coverage
👤 Personalization and Potential Buyer Recommendations
- Built user behavior-based embeddings and designed potential buyer recommendation systems
- Designed and operated A/B testing infrastructure for vector-based candidate generation and recommendation result evaluation
🗺️ H3-based Geographic System Implementation for North America
- Applied Hexagonal Hierarchical Spatial Indexing (H3) to implement regional system for North American regions
- Designed H3 data backfill and Rake tasks for multi-country deployment (JP/US/CA)
🛠️ Admin Tools and Monitoring System Development
- Developed Admin dashboard (PgVector Viewer) for recommendation system experiment result visualization
- Provided metrics screens based on daily indicators (clicks, conversion rates, etc.) to support business decision-making
🚀 CI/CD and Deployment Automation
- Designed and automated deployment pipelines based on GitHub Actions
- Configured multi-stage deployment for alpha/prod environments with automated rollback
🌍 Global Service Expansion Support
- Implemented country/region-specific parameter handling and branching for Japanese and North American market expansion
- Customized JP/CA/US-specific content and recommendation features
🧪 Experiment-driven Development Culture Participation
- Participated in designing and interpreting results from multiple experiments including ad recommendations, post recommendations, and potential buyer recommendations
- Extensive experience in flexible handling of feed/notification logic considering experiment states and performance optimization
Nov 2017 – Nov 2019, Seoul, South Korea
- Built and managed a team of 18 engineers for medical AI products.
- Led backend redesign for Lunit INSIGHT, reducing latency by 40% and improving integration for hospital partners.
- Delivered full-stack features including an in-house annotation tool and deployment system.
- Integrated with Fujifilm REILI platform for global distribution.
- Improved engineering processes by introducing structured workflows (Jira, Confluence, Notion).
- Speaker at DEVIEW 2018: “Data Engineering for Digital Pathology AI”
Sep 2016 – Oct 2017, Seoul, South Korea
- Rebuilt and launched Fund101 (small loan platform) from scratch.
- Developed and maintained multiple web/mobile services (Goodeats, Sirjuseyo, Autoup) under tight startup timelines.
- Delivered critical B2B integrations for prop-tech backoffices and internal sales tools.
Jul 2013 – Sep 2016, Seongnam, South Korea
- Main developer for KakaoTalk’s Notification Center and User Profile backend systems.
- Delivered in-app browser widget and improved SMS reachability with dynamic vendor routing.
- Led A/B testing and UX improvements for KakaoTalk profile feed layout across 10M+ users.
- Proposed and developed foundational components adopted across Kakao services (Brunch, Story, Music).
- DEVIEW 2018 – Data Engineering for Digital Pathology AI
- Startup Job Festival 2019 – Life of a Startup Developer: From Kakao to Lunit
- Backend: Python (Django), Ruby on Rails, PostgreSQL, MySQL, Redis, AWS
- Frontend: JavaScript, React, HTML/CSS
- Others: OAuth2, RabbitMQ, Zookeeper, Git, CI/CD, System Design, Large-scale Architecture
KAIST – M.S. in Web Science and Technology Aug 2013, Daejeon, South Korea
Korea University – B.S. in Computer Science Feb 2011, Seoul, South Korea
DART: An Efficient Method for Direction-aware Bichromatic Reverse k Nearest Neighbor Queries, Proc. of the 13th International Symposium, SSTD 2013, Munich, Germany, August 21-23, 2013.
http://link.springer.com/chapter/10.1007%2F978-3-642-40235-7_17
Ads by Whom? Ads about What? Exploring User Influence and Contents in Social Advertising, Proc. of the ACM Conference on Online Social Networks (COSN 2013), October 2013.
http://dl.acm.org/citation.cfm?id=2512950
DART+: Direction-aware Bichromatic Reverse k Nearest Neighbor Query Processing in Spatial Databases, Journal of Intelligent Information Systems: Volume 43, Issue 2 (2014), Page 349-377
http://link.springer.com/article/10.1007%2Fs10844-014-0326-3
METHOD FOR PROVIDING CONTENT, CONTENT PROVIDING SERVER FOR PERFORMING THE PROVIDING METHOD AND METHOD FOR RECEIVING CONTENT, USER DEVICE FOR PERFORMING THE RECEIVING METHOD, South Korea, 10-2013-0162897, Applied on May 28, 2015
METHOD FOR DISPLAYING WIDGET FOR EXTENSION SERVICE, AND DEVICE FOR PERFORMING THE METHOD, South Korea, 10-2015-0145829, Applied on September 12, 2017
METHOD FOR PRIVACY-SAFE COMMUNITY COMMUNICATION USING MESSENGER BOT SYSTEM, South Korea, 10-2015-0061679, Applied on September 29, 2017
METHOD AND APPARATUS FOR RECOMMENDING PHOTO COMPOSITION, South Korea, 10-2014-0062493, Applied August 25, 2016
어노테이션 작업 관리 방법, 이를 지원하는 장치 및 시스템, South Korea, 10-2018-0137355, Submitted on November 9, 2018