Junhwan Seok
Seoul, South Korea0
Backend & AI Engineer | Python · FastAPI · LangGraph · PostgreSQL | Built a multi-agent LLM backend and cut its running cost 76% | CS senior @ Kookmin Univ · Founder @ Stocky | Seeking US SWE internships
Backend engineer and AI systems builder shipping production applications. Focused on cost-efficient LLM pipelines, data infrastructure, and making architecture decisions that stick.
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Projects
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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.
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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.
Experience
Founder & Backend / AI Lead
StockyMar 2026 — 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.
Military Service
Republic of Korea Air ForceMay 2023 — Mar 2025
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Team Lead
CARRIOSep 2025 — Dec 2025 · 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.
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Developer
Seoul-in-Culture TeamJan 2025 — Dec 2025 · 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.
Education
Kookmin University
Bachelor of Engineering in 소프트웨어학과
Mar 2021 — Aug 2027
One of 8 students selected for Kookmin–Irvine global program; exchange study at Westcliff University, Irvine, CA (Sep 2026 – Feb 2027)
Korea Data Agency
SQLD (SQL Developer)
May 2026 — May 2026
Credentials
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Honor or award
Grand Prize (최우수상), 2026 KMU AI Startup Competition
Kookmin University Industry-Academic Cooperation Foundation
Issued Aug 2026
Top prize among university startup club teams, awarded by the Industry, Academic Cooperation Foundation with a KRW 2,000,000 grant. Recognized for Stocky, an AI financial-literacy platform for young generations
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Course
SQLD (SQL Developer)
Korea Data Agency
Issued May 2026
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Skills
백 엔드 웹 개발CI/CD아마존 웹 서비스(AWS)SQLRabbitMQ사업전략Software ArchitectureGitLarge Language ModelsPostgreSQLFastAPIPythonJavaSpring Boot 3.5SQLAlchemy 2.0Alembic