# Jonghyeon Ham

**Founder/CEO @ refresh.cv** — United States

Career Archetype: **Frontier Artisan** (RS-MX) — One of the first Frontier Artisans on Saywise

## Links

- LinkedIn: https://linkedin.com/in/jonghyeon-ham

## Experience

### Founder/CEO, refresh.cv (2024-10 – present)
대한민국 · refresh.cv - Drove zero-to-one across product, architecture, full-stack engineering, UX design, data analytics, and GTM/sales - Shipped resume editor with agent-based resume authoring, revision, and feedback - Launched resume scoring and feedback based job description - Delivered resume web templates and resume card components

### Server Developer, Viva Republica (Toss) (2023-03 – 2024-10)
Gangnam District, Seoul, South Korea · Toss Ads - Built and operated ad platform used in 15M+ MAU Toss app for campaign execution, review, and performance - Implemented ad performance ingestion/aggregation (impressions, clicks, plays) with Kafka, Druid, Impala - Implemented real-time CPM/CPC billing; ensured data integrity at scale with local cache + flush pattern - Contributed to settlements, agency commission payouts, and tax invoice issuance - Shipped ad account/group systems and integrated with Toss Business Display Ads product (monthly 10B+ KRW scale) - Contributed to eCPM-based ad recommendation and ranking improvements, driving >1B KRW monthly uplift - Implemented multiple optimization strategies to minimize ad refresh and serving latency, improving both UX and fill rate. - Implemented CPC (cost-per-click) and CPM (cost-per-mille) billing logic end-to-end for our ad serving pipeline. - Built real-time dashboards and alerting to monitor impressions, clicks, and spend in production, catching ad-serving incidents before they impact revenue Live Shopping - Optimized performance with tens of thousands of peak RPS without degrading UX using Local Cache, Redis and Kafka optimizations - Authored article on handling large-scale traffic without adding servers (https://toss.tech/article/monitoring-traffic) Credit Score Board - Built product aligned to financial context and user comprehension Benefits Tab (8M+ DAU) - Shipped Lucky Quiz, Lucky Lottery, Money Alerts, and Weekly Missions - Owned product development and operations from advertiser and user perspectives

### Co-Founder, Lead Software Developer, 트랜스버스(Transverse Inc.) (2020-11 – 2023-03)
대한민국 · founding team; leading product roadmap and led a 10-engineer team Evoclass: real-time video conference platform - Implemented WebRTC SFU with Mediasoup and high-performance socket servers using uWebSockets - Built server orchestrator and demand forecasting to reduce streaming cost and ensure efficiency - Created container-based load testing to guarantee real-time video/audio QoS and performance - Delivered real-time STT and translation via browser-native APIs - Built AI-powered video effects: background blur, virtual background, face morphing Learning Management System - Designed and implemented system architecture - Integrated with the video platform to enable AI-driven learning features

## Education

### Undergraduate in Computer Science, Korea Advanced Institute of Science and Technology (2020-03 – 2027-02)
- Admitted via special talent track - Developer, SPARCS student open-source club (sparcs.org)

### High School, Korea Digital Media High School (2017-03 – 2020-02)
- Admitted via contest winner track (KOI) - Graduated 1st in IT Literacy Certification Program

## Projects

### Baseweb, Uber
- Fixed an error in the official documentation - Pull Request #4355

### neis-counter
- Product Owner & Maintainer - Served 500k users in the last 12 months; used by ~1 in 10 Korean high school students

### NeuralAction
- Product Owner & Maintainer - A Real-time and Accurate Gaze Tracking Application for a More Natural Human-Computer Interaction with User Interface

## Skills

Kotlin, 스프링 프레임워크, WebRTC, Backend, Frontend, DevOps, Machine Learning, 리서치, 파워포인트, 자바, C#, C, Python, Flask, PHP, Node.js, MySQL, Docker, 아마존 웹 서비스(AWS), Visual Basic .NET, WPF, Zeplin, Photoshop, Illustrator, After Effect, 3D 스튜디오맥스, UI 디자인, UX 디자인, Socket.io, HTML5, CSS, Javascript, JQuery

## Credentials

- **1st place, OpenResource Hackathon Seoul** — Common Computer Inc, AI Network (issued 2019-12)
- **Talent Award of Korea** — Ministry of Education (issued 2018-11)
- **Grand Award 4th place, Intel International Science and Engineering Fair (ISEF)** — Intel, Society for Science (issued 2018-05)
- **1st, Korea Youth Science Creativity Challenge (ISEF-K)** — National Information Society Agency (issued 2018-02)
- **Gold Medal, Korea Olympiad in Informatics (KOI)** — Ministry of Science and ICT (issued 2017-11)
- **Large-Scale Traffic Without Adding Servers**
- **Rehearsal: Designing Systems for AI Interviews**

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Source: https://saywise.com/jhham (last modified 2026-08-09T16:50:19.204Z)