Portfolio
KOEN

Software engineer focused on problem-solving and the completeness of services without limiting tech stack. Actively contributes from the planning stage to prioritize user convenience. Currently responsible for the overall billing and user-side services across multiple MSA environments.

Experience

LG Uplus VoltUp

Sep 2024 — Present

Tech Innovation Tribe, Back-end

Billing - Improved payment and arrears-handling reliability with DLQ and multi-stage unpaid batches Promotions (coupon/points) - Improved customer retention User-side - Owned vehicle lookup, PnC (Plug & Charge) authorization, user-side backend, and the mobile app DX infrastructure - Standardized AI workflows and applied CI/CD integration and automated documentation

Kakao Style

Jun 2022 — Sep 2024

Pricing System, Back-end

Final pricing service, product matching, Zigzag membership new development and migration, and shopping EP integrations (Naver Shopping / Google Shopping). Pipelines for external price collection and competitive position automation.

Storelink

Mar 2021 — Jun 2022

R&D Engineer

Product-data collection and keyword-ranking analysis platform Developed AdLink, Uzzit, Pugshop, and Friday

Whatap Labs

Mar 2019 — Mar 2021

Front-end Engineer

Frontend development for monitoring dashboards across infrastructure, JVM applications, and Kubernetes.

Hamschout

Aug 2017 — Aug 2018

SW Engineer

Developed the Itfluencer platform matching influencers with businesses.

OpenBridge

May 2016 — Jul 2017

SW Engineer

Developed AlarmTalk (alarm + chat), Potion (photo editing + missions), and the OpenBridge web platform.

Projects — LGU+ VoltUp

Led payment design from the start; expanded from a single payment flow into a modular structure that supports multiple payment vendors, and improved payment-state consistency and failed/unpaid payment recovery through a layered arrears-management system.

KotlinSpring BootSpring BatchGCP Pub/SubCloud SQL

Coupon & point promotion platform buildout and enhancement

Coupon: Jul 2025 / Points: Aug 2025 — Present

Built a reusable coupon and points backend for partner-driven promotions such as Nexen, Toyota, and Bluemembers, including coupon-pack payment-vendor restrictions across issuance, lookup, usage, and admin management.

KotlinSpring BootMySQLJPA

User-side Backend

Jul 2025 — Present

Developed core user-side backend features including KakaoT account/payment integration across 4 MSAs, PnC (Plug & Charge) auto-charge, and unpaid-charge monitoring.

KotlinSpring BootGCP Pub/SubFlyway

Led Flutter hybrid delivery for 2.0; designed WebView-native bridge flows and core app paths such as QR scanning, permissions, push notifications, and forced updates.

FlutterGradleFCMML KitCrashlytics

Built a Chrome Extension that recreates app-dependent flows in the browser to reduce app-attachment validation delays, then extends into replayable single-API operational corrections not supported by Admin.

TypeScriptChrome ExtensionVitestGitHub Actions

Redesigned card-state management for the Ministry of Climate, Energy and Environment public roaming integration and added retry/monthly resync paths so baseline data can recover after missed events or transient failures.

KotlinSpring BootGCP Pub/SubSpring Batch

AI-first reviews, mobile CI/CD hardening, remote Gradle cache, iOS TestFlight automation, obfuscation policy, Firebase distribution, and internal Admin API standards.

Gemini APIGitHub CopilotClaude CodeCursorAntigravityFirebaseDockerGradleWorkload Identity

Projects — Kakao Style (2022.06 — 2024.09)

Mobile IP Pool Proxy Infrastructure & Dynamic Pricing

Jan 2024 — Sep 2024

Built a mobile IP pool proxy infrastructure to bypass crawling blocks and automated a dynamic pricing pipeline based on price competitiveness.

DockerMitmProxyK8SADBNode.jsKotlinSpring BatchAWS Athena

Overhauled 1:1 matching to an N:M structure to match identical products across all stores and types.

KotlinSpring BootSpring BatchDGS Framework(GraphQL)MySQLSpring KafkaAWS Athena

Unified scattered pricing logic into a single API so coupons, promotions, and other benefits follow one contract.

KotlinSpring BootDGS Framework(GraphQL)

Membership & Mileage Migration

Apr 2023 — Jun 2023

Redesigned membership tiers for retention and migrated the legacy membership service to Spring Boot.

KotlinSpring BootSpring BatchDGS Framework(GraphQL)JPAMySQLKafka

Enhanced price competitiveness of Zigzag products for exposure on Naver Shopping price comparison.

KotlinSpring BootSpring BatchKafkaMySQL

Projects — Earlier experience

Friday analytics

Mar 2021 — Jun 2022

Backend development for commerce keyword analytics service.

KotlinSpring BootWebFluxR2DBCRedis

Whatap monitoring FE

Mar 2019 — Mar 2021

Developed integrated monitoring dashboards to visualize data collected from various agents (App, Server, DB, Container).

React.jsReduxTypeScriptAnt DesignWebPack

Influencer platform

Aug 2017 — Aug 2018

Developed an influencer marketing platform for campaign management and influencer matching.

React.jsReduxTypeScriptAnt DesignAxiosWebPack

AlarmTalk (Android)

May 2016 — Aug 2017

Social alarm service combining alarms and chat for mutual wake-up calls.

JavaAndroidRealmDBFCMGlideJedis

Potion (Android)

May 2016 — Aug 2017

Mission-based photo filter app where users earn points for printing photos.

JavaAndroidRealmDBFCMGlide

Personal Projects

Commit Map Personal Project

Ongoing

A map-based travel planning service built to share my travel plans and quickly draft route ideas.

AstroReactTypeScriptLeafletMarkdownGitHub Pages

Teddy Resume Personal Project

Ongoing

A personal resume service that manages multilingual resumes and project portfolio pages from a single YAML source across multiple layouts, optimized for print and PDF output.

AstroTypeScriptTailwind CSSYAMLhtml2canvasjsPDF

Other Activities

Kookmin SW-Centered University Mentor

Mar 2024 — Present

Mentored students with a focus on SW architecture, problem-solving strategy, and user-side flow optimization.

[Mentor Profile]

Codeit Backend Course Mock Interview Mentor

Sep, Dec 2025

Conducted technical and mock interview mentoring for backend developer bootcamp graduates.

Kernel360 Backend Mentor (1st ~ 5th cohorts)

Dec 2023 — Aug 2025

Participated as a mentor across the 1st through 5th cohorts, guiding collaboration-based projects that solved real company problems.

Kakao Tech Campus Backend Mentor (2nd)

Jun 2024 — Aug 2024

Participated as a mentor for the 2nd cohort of Kakao Tech Campus backend track.

Hanyang ERICA SW Startup Lecture

Feb 2024

Gave a talk on "Effective Backend" for the SW startup lecture series.

Boostcamp 8th Backend Mentor

Nov 2023 — Dec 2023

Mentored two iOS service project teams for Boostcamp.

Hanbit N MSA — Monitoring session

Dec 2023

Led the 9th session on Monitoring for Hanbit Media's seminar series.

Boostcamp 7th~8th Backend Reviewer

Sep-Oct 2022 / Sep-Oct 2023

Conducted campus meetings and code reviews for web backend campers (7th and 8th cohorts).

UbuCon Korea 2023 Speaker

Sep 2023

Presented on "Building a Development NAS using WSL".

SW University Joint Hackathon 2023 Mentor

Jun 2023

Provided FE/BE mentoring and career counseling as a hackathon mentor.

Programmers School JAVA Mentor (11th)

Mar 2023 — Apr 2023

Provided Q&A, code reviews, and video mentoring.

Gyeongbuk SW High School React Lecture

Sep 2022 — Oct 2022

Conducted a React lecture series (Explanation > Clone Coding > Project) for vocational high school students.

Ubuntu Korea Community Infra Manager

Mar 2018 — May 2021

Managed infrastructure (Forum, Wiki, ASK, Mail server) for the Linux community.

AngelHack 2020

2020

LiBi, a group-buying and inventory-discount service for local small businesses Winner of the Common Computer Prize (KRW 2.4M)

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