Hyeonjun Kil

PROFESSIONAL SUMMARY

Backend engineer with 3 years and 7 months of experience across 4 domains (Education, Healthcare, Clinical Trials, Gaming), achieving quantifiable results including 82% BigQuery cost reduction, complete resolution of clinical trial system Deadlocks, and contributing to major hospital contract acquisitions. Specialized in system design from monolithic to Event-Driven cloud-native architectures, creating long-term business value through root cause analysis and systematic solutions.

SKILLS

Languages: JavaScript, TypeScript, Java

Frameworks: NestJS, Express.js, Spring Boot

Databases: MySQL, Redis

AWS: Lambda, SQS, SNS, EventBridge, RDS, S3, RDS Proxy, ElastiCache

Infrastructure: AWS CDK, Serverless Framework

Monitoring: CloudWatch, DataDog, Grafana

WORK EXPERIENCE

GameDuo — DEV Team Server Developer

2025-01 - Present

Mobile game development and publishing company

82% BigQuery Cost Reduction: Storage Read API adoption ($6.25→$1.1 per TB)
Serverless Architecture: Event-Driven Architecture based AWS Lambda migration
Marketing Integration Platform: Google Ads/Meta/TikTok unified dashboard
Game Data Audit System: Repository abstraction-based balance change tracking

JNPMedi — Dev2 Team Docs Squad Backend Engineer

2023-06 - 2024-08

Clinical trial data management solution startup with 16B KRW cumulative investment

Complete Deadlock Resolution: Foreign key lock timing analysis preventing clinical trial notification failures
New Contract Contribution: User-organization 1:N structure enabling major hospital and pharma company contracts
Rapid MVP Launch: VDR 3 weeks, TMF 3 months emergency deployment meeting deadlines
Event-Driven Architecture: AWS SNS/SQS based system reliability improvement

Medgo — Dev Team Backend Engineer

2022-04 - 2023-06

Telemedicine and medication delivery platform startup with 300K cumulative downloads

Architecture Modernization: Express.js → NestJS transition for code consistency and type safety
Unified Authentication System: JWT-based subdomain session conflict resolution
Medical Service Automation: OCR + public API for automated prescription medication guidance
Real-time Optimization: Socket.IO Room targeting for network traffic optimization

SimpleHAN — Dev Team Backend Engineer

2021-07 - 2022-04

Custom software solutions SI company

Bulk Data Processing: Apache POI-based batch processing for hundreds of member records
Multi-country Unified Auth: JWT-based cross-domain login system
Deployment Automation: Travis CI-based CI/CD eliminating hosting costs
Legacy Integration: iframe-based PHP system non-disruptive feature extension