* Tech lead, responsibility of mentoring and training senior engineers, and managing best practices and the tech stack.* Key role in designing and implementing the core system for the BEN (BookingEngine).* Led the design and implementation of a proprietary DynamicBooking system, which resulted in a 1.3% revenue increase within just 4months.* Successfully built a new team from scratch for the MarketPlaceCore systems.* Led and actively involved in multiple cross-cutting projects.* Contributions towards the company's IPO.* Python, RoR (Ruby on Rails), AWS, K8S, CI/CD , and TechRadar

Shopkick is the app that rewards users for shopping in-store at over 270,000 major retail locations and online. Over 10M users are using this indispensable mobile shopping app to earn reward points and redeem for a wide selection of free gift cards. It is also the most-used in-store shopping app in the US. * Implemented mobile commerce features and third-party commission based commerce platform(Button, Amazon, Linkshare, and Commission Junction) integration system. This system includes most of Shopkick’s core technologies. * Implemented product searching system for shopping cart feature with Elasticsearch.* Implemented Recipe features to enabling save&like system with Cassandra.* Improved in-house experimenting(A/B testing) tools to accommodate more complex feature testing. * Maintained enormous backend systems to serve stable features to millions of users.* Provided technical training for newbie engineers as a technical staff.

PangYo is a carpool service in Gyeonggi-do Pan-Gyo Techno-valley that is biggest tech district in South Korea.• Developed with Ruby on Rails(API tier), Node.js(Socket.io for realtime location streaming tier), Git, Capistrano, Unicorn, Nginx, Redis(cache, pub/sub tier), ElasticSearch(search tier). See also http://readme.skplanet.com/?p=8872 (Korean ver)• Design and development all server side architecture of PangYo.• Managed the web application running on the amazon server farm.• PangYo video clip : https://www.youtube.com/watch?v=LSE5zvpcipA

me2day webservice (Desktop, Mobile) development• Me2day is the biggest microbloging SNS service in Korea and has 10million users.• Developed with Ruby on Rails, JavaScript (jQuery), Git, Capistrano, Unicorn, Nginx, Redis, Memcached• Managed the web application running on a server farm with 30 servers to maintain high availability of service.• Upgraded WAS (from Passenger) to Unicorn for non-stop deployment without obstacle. Complete a task by oneself.• Optimized mobile webview (maximum 400 thousand page view) page load speed by 30% with incremental piggyback technology.• Increased deployment performance by 25% after 2 weeks of work by using multi thread batch.• Have stepped in on a sub-project (Band: http://band.naver.com) that had very tight schedule (4 weeks) and shipped them on-time.• Developed time based blocking module using redis for blocking Broute-force attack from abroad.

Mople• Mople was a micro messaging SNS service (hybrid iOS application).• Led a team on the project.• Developed from iOS to API server.• Mople iOS application was based on single-page web.

Interworking SNS web service for Aion• Aion (have 250 thousand concurrent users) was global scale MMORPG game.• Developed using Java, Spring, Hibernate, MySQL, sitemesh technology• Worked with a team of 13 on this project. • Developed comment server side API module.Shindig, Opensocial gadget• Shindig is java based Opensocial opensource framework. • Developed OpenSocial gadget alone.• Applied SNS social gadgets to OpenSocial-based prototype.• Applied gadgets to external OpenSocial support platform (hi5, Myspace).• Benchmarked API for other OpenSocail application services (hi5, orkut, MySpace)• Was master of Shindig specification.WoC (Winter of Code) site• WoC2007 was hosted by NCsoft to promote open-source software, similar to Google’s SoC (Summer of Code).• Developed and managed using Ruby on Rails, MySQL, jQuery on CentOS.• Developed it alone from client (HTML,CSS) to server (Ruby on Rails, WAS setup, etc.)API Center and mashup center• API center is NCsoft Openmaru OpenAPI authenticated web service. Mashup center is gallery of mashups. • Developed it alone from client (HTML,CSS) to server (Ruby on Rails, Was setup, etc.)• Integrated Open API to authenticated (OAuth) web service. Support for OAuth authentication modules for each service.• Adopted the Oauth standard in Korea for first time.iSpringNote• iSpringnote was an iOS application for springnote.com (a note taking service, similar to Evernote). • Developed it alone.• This was a very early time to develop iPhone applications because the iPhone was not officially imported to Korea at the time. There also was not a lot of information on iPhone application development and only API documents. It was pretty difficult, but I achieved my goals and completed the application.