▶ Heavily refactored the financial search service core while migrating its stack from ES5 to ES7: rearranged layers, fixed ambiguities in query grammar/plans, sanitized data across interfaces, cleaned rotten codes, etc. | Flask/Python, Java (for custom ES plugin), C++ (for proprietary vector DB), Elasticsearch, Kafka & MySQL▶ Launched B2C version of the service: added an email-based CIAM, credit card payment/billing, monitoring, customer services and admin features, etc. | FastAPI/Python, ...▶ Containerized dev env. and participated in the preparation/adoption of K8s. | Docker, Kubernetes▶ Carried out the operation/maintenance of the various microservices and data-crawling pipelines.

▶ Participated in the development, operation, and maintenance of a specialized L7 load balancing service which consists of 600+ nodes worldwide and acts as a front line of the LINE global instant messenger. | Erlang, C/C++ & Python/Linux▶ Identified lingering issues of the above service and made multiple enhancements: ① dockerized dev env. + CI pipelines, ② sanitized dependency management, ③ fixed provisioning procedures to become declarative & repeatable, ④ rewrote key modules—HTTP/2 HPACK, connectivity controller, log enricher + forwarder, etc.

▶ Designed an online item auction service for the mobile action RPG Lost Kingdom™ and developed its batch-processing auction broker to match & resolve outstanding orders. | Spring(Boot)/Java/Linux & MySQL▶ Led a total conversion project of the above game title into a global-ready service, which ① covers a wide range of geographic areas, ② has a resilient PVP backend, ③ retains enough flexibility for future content updates. Cancelled due to a less-than-good market performance of the original title. | Go/Linux, C#/Mono & MySQL▶ Managed an overseas collaboration project for the mobile action RPG Blood Tales (provisional), provided security reviews & performance guides for its game server development. | C#/.NET & MySQL

▶ Led the pilot project building ALLWIN™ iOS app, designed all backend services and developed its patented auction server. (Patent US8478657, US8799105) | Django/Python/Linux & PostgreSQL▶ Managed the mobile web service project for ALLWIN™, designed most of its backend services and built the billing server. | Spring(Boot)/Java/Linux & JPA-Hibernate over Aurora DB (MySQL clone)

▶ Took over the main server developer role for the mobile arcade action game Wind Runner™, developed its season 2 update. | PHP/Apache/Linux & MongoDB▶ Led the server-side development of the mobile PVP-focused action game Iron Slam™, developed its game server (Django/Python/Linux & MongoDB) and PVP server (VC++/Windows).

▶ Designed and built a few reusable components: a generic lobby-room server framework for mobile game services utilizing the latest C# async-await capabilities, an easy-to-use Unity™ Asset Bundle packaging pipeline to control their dependencies and speed up the deployment.▶ Developed game servers for the mobile arcade racing game Gods of Speed (provisional) (C#/Windows) and the mobile action RPG Dungeon Gate™ (C++/Linux, Lua & MySQL).

▶ Participated in the maintenance and enhancement project for the various PC online web-board (Poker-like) game servers. | VC++/Windows & Oracle▶ Helped stabilizing a newly built game servers for the PC online puzzle game Puzzle Bubble™, provided security analysis, performance optimizations and bug fixes: e.g. concurrency control & locking problems.▶ Designed and developed a generic C++ lobby-room server framework for mobile game services, later abandoned prematurely due to the company's financial crisis.

▶ Developed an on-demand image composition server for Hangame™ avatar/portrait service. | Apache-Tomcat/Java/Linux▶ Developed instant messenger servers for the online community service Entoi™. | C++/Linux & Oracle▶ [Dispatched to NHN China, JAN 2004 ~ SEP 2004] Developed backend game servers for China service, built key system libraries, mitigating consistency problems between long-distance IDCs. | C++/Linux▶ Participated in the maintenance and enhancement project for Hangame™ Server Platform, developed P2P networking libraries utilizing the UDP hole-punching technique. | VC++/Windows & Oracle▶ [Dispatched to NHN Japan, MAR 2006 ~ OCT 2006] Led the publishing projects of the online sports game Free Style™ and the MO-RPG Arad Saga (Dungeon and Fighters)™.▶ Participated in the design and development of the Hangame™ Publishing Platform, made various backend APIs & SDKs for game developers: e.g. authentication. | VC++/Windows

▶ Developed a web-based rich e-mail service DearYou™ and a community service Back2School™ – built their websites (ASP/IIS/Windows & MS-SQL) and backend daemons (VC++, COM+).▶ Developed home networking applications for primitive home automation. | VC++, UPnP