# Junhwan Seok

**Founder, Backend & AI Lead at Stocky** — Seoul, South Korea

> Backend engineer and AI systems builder shipping production applications. Focused on cost-efficient LLM pipelines, data infrastructure, and making architecture decisions that stick.

Career Archetype: **Launchpad Navigator** (HS-DG) — One of the first Launchpad Navigators on Saywise

## Links

- LinkedIn: https://linkedin.com/in/junhwan-dev
- junhwan.me: https://junhwan.me
- github.com/clark1015: https://github.com/clark1015

## Experience

### Founder & Backend / AI Lead, Stocky (2026-03 – present)
Seoul · Built and shipped a production ETL pipeline ingesting global market news every 15 minutes with embedding and event clustering. Reduced daily LLM spend by 76% through model routing, prompt caching, and batching. Replaced an LLM classifier with deterministic logic plus embedding fallback, improving accuracy from 19% to 46% at a quarter of the cost. Moved financial computations from LLM to rule-based code, eliminating fabricated numbers and cutting the core module from 1,458 to 365 lines.

### Team Lead, CARRIO (2025-09 – 2025-12)
Seoul · Led auth, data modeling, and API backbone for an AI writing assistant with four engineers. Owned all Alembic migrations and contributed 63 backend commits, the most on the team. Designed two three-agent LangGraph pipelines for source extraction and draft generation.

### Developer, Seoul-in-Culture Team (2025-01 – 2025-12)
Seoul · Built a batch scheduler ingesting Seoul Open Data into MongoDB on a fixed cycle. Owned the meeting-domain API. Developed for the Seoul Open Data public-data competition.

### Military Service, Republic of Korea Air Force (2023-05 – 2025-03)

## Education

### SQLD (SQL Developer), Korea Data Agency (2026-05 – 2026-05)

### Bachelor of Engineering in 소프트웨어학과, Kookmin University (2021-03 – 2027-08)
One of 8 students selected for Kookmin–Irvine global program; exchange study at Westcliff University, Irvine, CA (Sep 2026 – Feb 2027)

## Projects

### WinkBootCamp, a Spring Boot authentication system
Authentication Service · Split one Redis instance across three lifetimes: 5-minute verification-code TTL, 14-day refresh tokens, and a blacklist for revoked access tokens. Moved email delivery onto RabbitMQ to prevent SMTP latency from blocking the auth API. Built the full deploy path from Docker Compose through GitHub Actions to AWS EC2 with Spring Security, JWT (15-min access / 14-day refresh), and Kakao OAuth2.

### Seoul-in-Culture
Batch scheduler for Seoul Open Data · Ingested Seoul Open Data on a fixed cycle into MongoDB. Owned the meeting-domain API. Built for the Seoul Open Data public-data competition.

## Skills

백 엔드 웹 개발, CI/CD, 아마존 웹 서비스(AWS), SQL, RabbitMQ, 사업전략, Software Architecture, Git, Large Language Models, PostgreSQL, FastAPI, Python, Java, Spring Boot 3.5, SQLAlchemy 2.0, Alembic, REST API design, pgvector, Redis, MongoDB, ETL pipeline design, Docker, GitHub Actions, AWS RDS, LangGraph, OpenAI, Claude APIs, model routing, prompt caching

## Credentials

- **Grand Prize (최우수상), 2026 KMU AI Startup Competition** — Kookmin University Industry-Academic Cooperation Foundation (issued 2026-08)
- **SQLD (SQL Developer)** — Korea Data Agency (issued 2026-05)

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Source: https://saywise.com/member1738 (last modified 2026-09-30T01:50:05.542Z)