Portfolio
KOEN

Software engineer focused on solving operationally complex problems and delivering reliable, polished products. I contribute from product planning through production operations, with customer experience as a primary design constraint. At VoltUp, I work across billing, customer-facing, charging, and roaming services in a microservices architecture.

Experience

LG Uplus VoltUp

Sep 2024 — Present

Software Engineer

EV charging joint venture between LG U+ and Kakao Mobility.

  • Payments & Billing — Built multi-provider payment architecture and dead-letter queue (DLQ) recovery, preventing duplicate charges with database-backed atomic approval locks
  • Promotions & Customer Products — Built reusable coupon and points systems, customer-facing backend services, and the VoltUp mobile app
  • Reliability — Standardized graceful Pub/Sub shutdown and isolated external API failures across microservices
  • Developer & AI Tooling — Built specialist-agent routing, first-pass log diagnosis, shared CI/CD workflows, and automated technical documentation

Kakao Style

Jun 2022 — Sep 2024

Backend Engineer, Pricing Platform

Built external-to-internal product matching, dynamic pricing, and the Final Pricing API Developed Catalog Engine Page and lowest-price update pipelines for Naver Shopping and YouTube Shopping

Storelink

Mar 2021 — Jun 2022

R&D Engineer

Built product-data collection and keyword-ranking analytics services Developed AdLink, Uzzit, Pugshop, and Friday

WhaTap Labs

Mar 2019 — Mar 2021

Frontend Engineer

Built monitoring dashboards for infrastructure, JVM applications, databases, and Kubernetes environments.

Hamschout

Aug 2017 — Aug 2018

SW Engineer

Built Itfluencer, a platform that connects advertisers with influencers for campaign delivery.

OpenBridge

May 2016 — Jul 2017

SW Engineer

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

VoltUp Projects (Sep 2024 — Present)

Led the payment service from initial architecture through production delivery, evolving a single-provider flow into a modular multi-provider platform. Added database-backed approval ownership and layered recovery to prevent duplicate charges and move failed or unpaid transactions into traceable, recoverable states.

KotlinSpring BootSpring BatchGCP Pub/SubCloud SQL

Coupon and Points Promotion Platform

Coupon: Jul 2025 / Points: Aug 2025 — Present

Built reusable coupon and points services for partner campaigns including Nexen, Toyota, and Bluemembers. Applied coupon-level payment-method restrictions consistently across issuance, lookup, redemption, and operations-console workflows.

KotlinSpring BootMySQLJPA

Connected the customer app, coupon service, and operations console to issue monthly benefits for LG U+ VIP and VVIP members. Gave operations teams the lookup, eligibility checks, and assisted-issuance tools needed to resolve customer inquiries without manual engineering support.

KotlinSpring BootSpring BatchReactTypeScriptMySQLQueryDSLFeign

Built customer-facing backend services spanning four microservices, including Kakao T account and payment integration, Plug & Charge enrollment, failed-payment monitoring, and isolation of external-system failures.

KotlinSpring BootGCP Pub/SubFlyway

Led delivery of the Flutter-based VoltUp 2.0 app, designing its WebView-to-native bridge and core flows for QR scanning, permissions, push notifications, and mandatory updates.

FlutterGradleFCMML KitCrashlytics

Built a Chrome extension that reproduces app-dependent flows in the browser, removing the need to connect a mobile app for routine validation. Extended it with controlled API capture and replay for operational corrections not available in the operations console.

TypeScriptChrome Extension

Built Voltbot, an internal agent platform that routes employees to specialized agents based on intent, permissions, and agent availability. Developed an evidence-driven incident-diagnosis workflow that combines Cloud Logging, BigQuery, internal guidance, and code search across broken trace boundaries, then verified groundedness and cost improvements with an evaluation harness.

KotlinSpring BootReactTypeScriptWebSocketGCP Cloud LoggingGemini Native Function CallingGemini API (3.6 Flash)GitHub API

Redesigned card-state recovery and resynchronization for Korea's public EV-roaming network, and made long-running Kakao T partner batches safe to stop and migrate without overlapping executions.

KotlinSpring BootGCP Pub/SubSpring BatchRedis

Standardized recurring engineering work through automated first-pass reviews, shared CI/CD workflows, developer-environment tooling, documentation automation, and internal API conventions.

Gemini APIGitHub CopilotClaude CodeCursorAntigravityFirebaseDockerGradleWorkload Identity

Kakao Style Projects (Jun 2022 — Sep 2024)

Built a mobile proxy pool to keep product-data collection reliable under anti-bot restrictions, then automated dynamic pricing from competitor price comparisons.

DockerK8SNode.jsKotlinSpring BatchAWS Athena

Replaced a one-to-one model with many-to-many matching that links external marketplace products to internal catalog products across stores and product types.

KotlinSpring BootSpring BatchMySQLSpring KafkaAWS Athena

Final Pricing API

Dec 2023 — Sep 2024

Consolidated channel-specific pricing rules into one API so coupons, promotions, and other benefits follow a consistent contract.

KotlinSpring BootDGS Framework(GraphQL)

Membership Platform Migration

Apr 2023 — Jun 2023

Redesigned membership tiers and migrated the legacy service to Spring Boot without downtime.

KotlinSpring BootSpring BatchDGS Framework(GraphQL)JPAMySQLKafka

Built shopping-feed and lowest-price update pipelines that kept Zigzag products eligible for Naver Shopping price comparison.

KotlinSpring BootSpring BatchKafkaMySQL

Earlier-Career Projects

[Storelink] Friday Commerce Analytics

Mar 2021 — Jun 2022

Built backend services for commerce keyword and search-ranking analytics.

KotlinSpring BootWebFluxR2DBCRedis

[WhaTap Labs] WhaTap Monitoring Frontend

Mar 2019 — Mar 2021

Built unified monitoring dashboards for telemetry collected from applications, servers, databases, and containers.

React.jsReduxTypeScriptAnt DesignWebPack

[Hamshout] Influencer Marketing Platform

Aug 2017 — Aug 2018

Built an influencer-marketing platform where advertisers manage campaigns and creators participate in sponsored work.

React.jsReduxTypeScriptAnt DesignAxiosWebPack

[OpenBridge] AlarmTalk (Android)

May 2016 — Aug 2017

Built a social alarm app that combines alarms and chat so users can help wake one another.

JavaAndroidRealmDBFCMGlideJedis

[OpenBridge] Potion (Android)

May 2016 — Aug 2017

Built a mission-based photo app where users earn points and redeem them for photo prints.

JavaAndroidRealmDBFCMGlide

Side Projects

Clip Atlas (clip-indexer) — Media Tag Generator Personal Project

Ongoing

Built a CLI and local web media manager that scans media files, combining FFmpeg and multimodal LLM analysis for smart file renaming, tag sidecar storage, and browser-based file management.

GoFFmpeg / ffprobeGemini API (Multimodal)React / Web UI

Commit Map Personal Project

Ongoing

A map-based travel planner for drafting itineraries, visualizing routes, and sharing trip plans through one link.

AstroReactTypeScriptLeafletMarkdownGitHub Pages

Teddy Resume Personal Project

Ongoing

A multilingual resume and portfolio service that generates multiple layouts and print-ready PDFs from one YAML source.

AstroTypeScriptTailwind CSSYAMLhtml2canvasjsPDF

Other Activities

Mentor, Kookmin University SW-Centered University Program

Mar 2024 — Present

Mentored students in software architecture, problem-solving strategy, and flow design.

[Mentor Profile]

Mock Interview Mentor, Codeit Backend Program

Sep and Dec 2025

Provided technical and mock-interview coaching for backend program graduates.

Backend Mentor, Kernel360 (Cohorts 1–5)

Dec 2023 — Aug 2025

Mentored five cohorts on team projects solving real company problems.

Backend Mentor, Kakao Tech Campus (2nd Cohort)

Jun 2024 — Aug 2024

Mentored the second cohort of the Kakao Tech Campus backend track.

Guest Lecturer, Hanyang University ERICA Software Startup Program

Feb 2024

Delivered an "Effective Backend" lecture for a software startup program.

Backend Mentor, Boostcamp Web·Mobile (8th Cohort)

Nov 2023 — Dec 2023

Mentored two iOS service project teams.

Speaker, Hanbit N Microservices Monitoring Session

Dec 2023

Presented the monitoring session in Hanbit Media's MSA seminar series.

Backend Code Reviewer, Boostcamp Web·Mobile (7th–8th Cohorts)

Sep 2022 — Oct 2023

Led campus meetings and code reviews for web-backend campers across two cohorts.

Speaker, UbuCon Korea 2023

Sep 2023

Presented "Building a Development NAS Using WSL."

Mentor, 2023 SW-Centered Universities Joint Hackathon

Jun 2023

Provided frontend and backend technical mentoring and career guidance.

[Mentor Profile]

Java Mentor, Programmers School (11th Cohort)

Mar 2023 — Apr 2023

Provided technical Q&A, code reviews, and remote mentoring.

Guest Lecturer, React Course at Gyeongbuk Software High School

Sep 2022 — Oct 2022

Taught a hands-on React course progressing from concepts to a final project.

Infrastructure Manager, Ubuntu Korea Community

Mar 2018 — May 2021

Maintained the community forum, wiki, Q&A, and mail infrastructure.

Award Winner, AngelHack Seoul 2020 (Common Computer Prize)

2020

Developed LiBi, a local group-buying platform, and received the Common Computer Prize.

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