Summary
Overview
Work History
Education
Skills
Software
Certification
Interests
Timeline
Generic

YoungJun Lee

Programmer
Seoul,11

Summary

A Senior Developer specializing in AI & Machine Learning solutions deployment and database performance optimization across various platforms.
With deep expertise in Spring Boot & Microservices Architecture, I have significantly improved system reliability and efficiency while demonstrating strong problem-solving skills and an innovative approach.
My experience spans backend development, DevOps (CI/CD), and database optimization (MariaDB, PostgreSQL) across multiple industries.
Currently, I am focused on AI and machine learning-driven projects, developing data-driven solutions that enhance business operations.

Overview

20
20
years of professional experience
1
1
Certification
2
2
Languages

Work History

Freelance Senior Developer

Nostra AI, Inc.
09.2024 - 11.2024
  • Developed and deployed AI-powered solutions, integrating ChatGPT 4o and Claude Sonnet 3.5 to enhance automated English problem generation.
  • Designed and implemented a dynamic AI-driven prompt request system for Poolda, enabling flexible generation of customized English questions.
  • Built and maintained a full-stack web application, including backend (CodeIgniter 3, MySQL 8.0) and frontend (Vue.js, JavaScript).
  • Optimized AI-generated JSON processing to reduce errors and improve system reliability.
  • Implemented server infrastructure using Ubuntu 22.04, Apache 2.4, PHP 7.4, MySQL 8.0, and successfully migrated the Poolda database.
  • Reduced API costs by integrating manual AI processing methods, minimizing token-based expenses while maintaining high accuracy.
  • Led the development and deployment of scalable AI-powered solutions, ensuring seamless integration with OpenAI API.

Freelance Senior Developer

MyPlatform / SK Gas
11.2023 - 01.2024
  • Developed and integrated SNS login authentication for SK Gas, supporting Naver, Google, Kakao, and Apple logins.
  • Implemented SNS login request, authentication, connection, disconnection, and logout functionalities.
  • Developed user information synchronization and SNS login integration with existing authentication systems.
  • Worked with Java, JSP, Spring Boot, Oracle, MyBatis, jQuery to build robust authentication features.
  • Ensured seamless OAuth 2.0 integration and security compliance for SNS authentication services.

Freelance Senior Developer

InterSolution Technology / Samsung SDS
01.2023 - 08.2023
  • Developed and tested Java, Oracle, and WebLogic for Samsung SDS SCP migration project.
  • Upgraded Java 1.7 → 1.8, WebLogic 10.3.6 → 14c, and Oracle 11g → 19c to enhance system performance and stability.
  • Developed and maintained Samsung Electronics' mobile email management modules, including hweh, mtvh, ota, ptvh, smpl, sscm.
  • Worked with Java, Spring Framework, Oracle, and Anyframe 1.5.1 to ensure seamless system integration.
  • Collaborated with Samsung SDS project and operations teams to identify and resolve technical issues.
  • Conducted functional testing, fixed bugs, and deployed applications to SCP servers.

Freelance Mid-Level Developer

EHCore / SK Hynix
06.2022 - 12.2022
  • Developed and maintained Back-End APIs for SK Hynix Customer Collaboration System (CSP).
  • Implemented file upload/download, payment system, access control, and email notification features.
  • Collaborated with clients, PMs, and developers to analyze requirements and design solutions.
  • Developed multiple APIs for notice pages, search pages, and admin pages.
  • Worked with JavaScript, Spring Boot, MyBatis, Oracle to build and optimize the system.

Mid-Level Developer

Nostra AI, Inc.
12.2021 - 02.2022
  • Designed and developed an AI-powered web-based system for internal artificial intelligence solutions.
  • Led system analysis and architecture design to ensure scalability and performance.
  • Developed core functionalities using Spring Boot, MyBatis, and jQuery.
  • Implemented key AI system modules and integrated intelligent decision-making algorithms.
  • Worked remotely from Seongnam while collaborating with the Seoul-based team.

Mid-Level Developer

Persona AI, Inc.
09.2020 - 12.2020
  • Developed and designed an internal web-based system for AI-powered solutions.
  • Led system analysis and implementation, ensuring performance optimization.
  • Worked with Spring Boot, MyBatis, jQuery to build scalable web applications.
  • Implemented UI components and improved user experience through frontend enhancements.
  • Collaborated remotely from home while engaging with the Seoul-based development team.

Mid-Level Developer

Persona AI, Inc.
07.2019 - 06.2020
  • Developed and designed internal web-based systems, leading architecture and analysis.
  • Worked on multiple projects as a freelancer, supporting various development tasks.
  • Developed key backend functionalities using Spring Boot, MyBatis, and MySQL.
  • Implemented UI components and interactive features using jQuery and JavaScript.
  • Worked remotely part-time, collaborating with on-site team members in Seoul.

Freelance Mid-Level Developer

Woojooae Soft / Armed Forces Welfare Agency
09.2019 - 02.2020
  • Developed and maintained e-commerce and procurement systems for the Ministry of National Defense Welfare Agency.
  • Built and optimized internet shopping mall platforms for web and mobile users.
  • Led full-stack development for product sales, supplier selection, and logistics management platforms.
  • Designed and implemented front-end and back-end functionalities using Java, jQuery, MyBatis, Oracle, and eGovFrame.
  • Analyzed client requirements and contributed to system design and architectural planning.

Freelance Mid-Level Developer

IWay / General Insurance Association of Korea
06.2019 - 08.2019
  • Developed and maintained the website for the General Insurance Association of Korea’s (GIAK) Auto Accident Liability Dispute Mediation Committee.
  • Designed and implemented front-end and back-end functionalities using Java, jQuery, MyBatis, Oracle, and eGovFrame.
  • Built core modules for case management, dispute mediation, and data processing.
  • Analyzed client requirements and conducted system architecture planning.
  • Ensured seamless integration of eGovFrame with backend services for government-standard compliance.

Freelance Mid-Level Backend Developer

Made in Heaven / KT Hitel
03.2019 - 05.2019
  • Developed and maintained API services for the KT GIGA Genie BLE device platform.
  • Designed and implemented backend functionalities using Java, Spring Boot, PostgreSQL, and MyBatis.
  • Optimized data handling and database performance for BLE device communication.
  • Collaborated with KT Hitel’s project team to analyze customer requirements and system design.
  • Ensured seamless integration of APIs with KT’s IoT ecosystem.

Freelance Mid-Level Developer

AT Solutions / Made in Heaven & Flex
11.2018 - 02.2019
  • Developed and maintained the PASS certificate web platform for authentication services.
  • Built and optimized front-end and back-end functionalities using Java, Spring Boot, MyBatis, Oracle, and jQuery.
  • Designed and implemented experience pages and admin management systems.
  • Initially developed under Made in Heaven, later transitioned to Flex as a freelancer.
  • Collaborated with multiple teams to ensure seamless project continuity and feature enhancements.

Freelance Mid-Level Developer

Persona AI, Inc.
02.2018 - 12.2018
  • Developed and implemented a web-based internal system for enterprise solutions.
  • Led system analysis and database design to optimize data storage and retrieval.
  • Worked with Spring Boot, MyBatis, MySQL, Java, and jQuery to develop and maintain functionalities.
  • Implemented UI enhancements for improved user experience and performance.
  • Worked remotely part-time while collaborating with the Seoul-based development team.

Mid-Level Developer

Hanqae System / WEMAKEPRICE (WMP)
10.2017 - 06.2018
  • Developed and maintained web applications for WEMAKEPRICE (WMP) e-commerce platform.
  • Built mobile web solutions for T&C (투어&컬쳐) services, implementing JSP, Java, Spring, MyBatis, MySQL, and jQuery.
  • Developed and optimized API integrations for product purchase and order processing.
  • Led the development of the WMP Delivery 2.0 System using PHP, MySQL, NetBeans, and CodeIgniter, focusing on order error handling and fixes.
  • Worked on Homeplus SCM project, designing order processing and API-based logistics control.
  • Implemented SOAP and RESTful APIs for seamless e-commerce and logistics communication.

Freelance Mid-Level Developer

Persona AI, Inc.
07.2017 - 11.2017
  • Developed and implemented a web-based internal system for enterprise operations.
  • Led system analysis and database design to optimize data storage and processing.
  • Worked with Spring Boot, MyBatis, MySQL, Java, and jQuery to develop and maintain core functionalities.
  • Designed and optimized UI components for improved user experience.
  • Worked remotely part-time while collaborating with the Seoul-based development team.

Freelance Mid-Level Developer

Maduwoori English Academy
05.2014 - 05.2015
  • Developed and maintained an English vocabulary test website for educational use.
  • Designed system architecture and implemented database structures using MySQL and PHP.
  • Built responsive web interfaces with HTML, CSS, and JavaScript for improved user experience.
  • Ensured backend stability by optimizing SQL queries and PHP scripts.
  • Worked remotely from home while collaborating with academy staff for feature updates.

Software Engineer

I-Shift / Korea South-East Power (KOEN)
06.2012 - 09.2013
  • Developed and maintained the Korea South-East Power (KOEN) task management system.
  • Designed and implemented a web-based project tracking platform using Java, JSP, JSTL, Spring, MyBatis, and Oracle.
  • Developed the AmorePacific CSR portal, leading system architecture and database design.
  • Performed regular maintenance and feature enhancements for AmorePacific's social contribution platform.
  • Implemented AJAX-based UI enhancements for seamless user interactions.

Web Developer Intern

WorldBizNet
12.2010 - 05.2011
  • Developed and maintained an e-commerce platform for WorldBizNet.
  • Managed front-end and back-end development, implementing HTML, jQuery, MySQL, and PHP.
  • Optimized SQL queries to enhance database performance and site efficiency.
  • Contributed to UI/UX improvements, ensuring an intuitive shopping experience.
  • Worked with a cross-functional team to handle shopping mall operations and technical maintenance.

Software Engineer & System Administrator

WebCommunity
05.2006 - 07.2008
  • Developed and maintained the Education Pension Management System (EPMS) for military-affiliated religious organizations.
  • Integrated and managed EPMS for five religious groups: Assemblies of God, Methodist, Holiness, Baptist, and Presbyterian denominations.
  • Designed and optimized backend systems using Java, MS-SQL, and Servlets.
  • Developed front-end interfaces using JavaScript and SQL-based reporting tools.
  • Provided technical support and ensured system stability for pension management operations.

Software Engineer & Web Developer

SEMI Information Technology Co., Ltd.
03.2005 - 10.2005
  • Developed and maintained various web-based projects for corporate clients.
  • Designed and implemented the Prudential Life Insurance in-house training system.
  • Worked with Java, JSP, Servlets, and Oracle to develop and manage backend operations.
  • Enhanced front-end performance using HTML and JavaScript for seamless user experience.
  • Provided ongoing maintenance and feature upgrades to ensure system reliability.

Education

Master of Science - AI & Big Data

Seoul School of Integrated Sciences & Technologies
Seoul, South Korea
04.2001 -

Master of Science - Industrial Management Engineering

Hanyang University Graduate School of Engineering
Seoul, South Korea
04.2001 -

Bachelor of Science - Computer Engineering

Academic Credit Bank System (Korea)
South Korea
04.2001 -

Skills

Spring Boot & Microservices Architecture

Software

IntelliJ IDEA, VS Code, Docker, Kubernetes, GitHub Actions, Jenkins

Certification

Korean Engineer Information Processing License

Interests

AI & Machine Learning

Software Development Automation

DevOps & Cloud Computing

Frontend & UI Development

Video Production & Content Creation

Timeline

Freelance Senior Developer

Nostra AI, Inc.
09.2024 - 11.2024

Freelance Senior Developer

MyPlatform / SK Gas
11.2023 - 01.2024

Freelance Senior Developer

InterSolution Technology / Samsung SDS
01.2023 - 08.2023

Freelance Mid-Level Developer

EHCore / SK Hynix
06.2022 - 12.2022

Mid-Level Developer

Nostra AI, Inc.
12.2021 - 02.2022

Mid-Level Developer

Persona AI, Inc.
09.2020 - 12.2020

Freelance Mid-Level Developer

Woojooae Soft / Armed Forces Welfare Agency
09.2019 - 02.2020

Mid-Level Developer

Persona AI, Inc.
07.2019 - 06.2020

Freelance Mid-Level Developer

IWay / General Insurance Association of Korea
06.2019 - 08.2019

Freelance Mid-Level Backend Developer

Made in Heaven / KT Hitel
03.2019 - 05.2019

Freelance Mid-Level Developer

AT Solutions / Made in Heaven & Flex
11.2018 - 02.2019

Freelance Mid-Level Developer

Persona AI, Inc.
02.2018 - 12.2018

Mid-Level Developer

Hanqae System / WEMAKEPRICE (WMP)
10.2017 - 06.2018

Freelance Mid-Level Developer

Persona AI, Inc.
07.2017 - 11.2017

Freelance Mid-Level Developer

Maduwoori English Academy
05.2014 - 05.2015

Software Engineer

I-Shift / Korea South-East Power (KOEN)
06.2012 - 09.2013

Web Developer Intern

WorldBizNet
12.2010 - 05.2011

Korean Engineer Information Processing License

06-2006

Software Engineer & System Administrator

WebCommunity
05.2006 - 07.2008

Software Engineer & Web Developer

SEMI Information Technology Co., Ltd.
03.2005 - 10.2005

Master of Science - AI & Big Data

Seoul School of Integrated Sciences & Technologies
04.2001 -

Master of Science - Industrial Management Engineering

Hanyang University Graduate School of Engineering
04.2001 -

Bachelor of Science - Computer Engineering

Academic Credit Bank System (Korea)
04.2001 -

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