Oh Hyunji — Full-stack Developer
Full-stack engineer with deep expertise in Next.js, Nest.js, and AWS, delivering scalable, reliable, and AI-ready digital products.
Open Resume PDFImpact Metrics
Quantified outcomes from delivery, optimization, operations, and AI-enabled automation.
40%
Faster defect resolution
Improved triage, diagnostics, and test coverage, with AI-assisted automation.
4
Product surfaces delivered
Kiosk, mobile, web, and admin releases aligned to one roadmap.
4+ yrs
End-to-end delivery
From platform APIs to production-grade UI.
Selected Projects
A curated selection highlighting problem definition, execution, outcomes, and AI usage.
BusinessPlus CRM
Main-site redesign for a B2B IT consulting firm
Hanleeon Patent Consulting
Cafe24-based site refresh for a patent law firm
Inno3Dental Chat
Real-time group chat for a partner network platform
Inno3Dental Dashboard
Admin dashboard with reports, storage metrics, and analytics
Report Management
Report list and detail view with date and keyword filters
Account & Profile
Account settings and user profile management screens
Kiosk Payment Integration System
Delivery of a kiosk payment integration system
Case Studies
Selected engagements with explicit problem definition, solution, outcomes, and AI integration.
Kiosk Payment Integration
Problem: Payment flows were inconsistent across devices and connection states.
Solution: Delivered a C#/.NET HTTP plugin, hardened JS↔C# bindings, and implemented fallback handling.
Result: Stabilized /Auth and /Cancel flows with resilient device orchestration.
QR/Barcode Scanner Connectivity
Problem: Scanner data loss and inconsistent parsing in kiosk environments.
Solution: Implemented RS232 parsing, validation, and asynchronous UI synchronization.
Result: Improved scan accuracy and response feedback consistency.
Real-time Platform Features
Problem: High-traffic collaboration required reliable real-time messaging.
Solution: Implemented WebSocket messaging with Bull Queue and Redis session sharing.
Result: Sustained 1:N group chat with stable session continuity.
Waiting System Modernization
Problem: Peak-time traffic caused inconsistent ordering and operational recovery issues.
Solution: Implemented Redis atomicity with DB synchronization, session scopes, and fallback recovery flows.
Result: Delivered consistent sequencing, duplicate-prevention, and reliable recovery under load.
Settlement Statement Site
Problem: Manual settlement documentation created operational delays and inconsistencies.
Solution: Built an AI-assisted internal settlement site with standardized workflows and deployment automation.
Result: Improved turnaround time and reduced manual reconciliation effort.
Experience
Roles, scope, impact, and AI application across products and platforms.
Queen's Smile
Full-stack Developer2025.09 ~ Present · Present
- Delivered kiosk, mobile, web, and admin services across the product suite
- Built a queueing project using Nest.js and Redis
- Designed and implemented a real-time waiting system backend for register–call–entry flows (NestJS, Redis, MySQL)
- Developed and deployed an internal settlement statement site with AI support
- Developing features with Java, Nest.js, and Next.js
- Provided operational support and continuous feature enhancement
📦 Tech Stack: Java, Nest.js, Next.js, Redis, Kiosk, Mobile, Web, Admin
Queen's Smile
Contract Developer2025.07 ~ 2025.07 · 1 weeks
- Delivered QR and barcode scanner integration
- Handled RS232 serial communication via SerialPort and event-based ingestion
- Implemented prefix-based parsing for variable-length payloads
- Applied regex validation and data sanitization for scans
- Synchronized scanner input with React kiosk UI asynchronously
- Transmitted scan data via HTTP and reflected responses in UI state
- Implemented fallback alerts and error handling for device disconnects
📦 Tech Stack: C#, WinForms, SerialPort, Regex, JavaScript, React, HTTP
Queen's Smile
Contractor2025.06 ~ 2025.06 · 2 weeks
- Delivered kiosk payment integration and production setup
- Built a C#/.NET HTTP plugin for tPayDaemon
- Optimized HttpClient configuration with SSL and JSON bindings
- Stabilized payment requests on /Auth and /Cancel endpoints
- Embedded Chromium (CefSharp.WinForms) and implemented JS↔C# bindings
- Configured JavascriptObjectRepository and Chrome API communication
- Integrated EMV card terminals via serial port with ACK handling
- Implemented POS autofill, debugging logs, and fallback handling
📦 Tech Stack: C#, .NET Framework, CefSharp, HttpClient, JSON, WinForms, SerialPort, Windows Registry
Inno3D
Platform Team Senior Researcher2022.04 ~ 2025.05 · 3 years 2 months
- Designed and delivered real-time ordering, 3D file viewing (three.js), login persistence, and partner network features
- Deployed high-availability services on AWS EC2, RDS, and load balancers
- Implemented JWT authentication with OTP and Nest.js Guards for data protection
- Shared sessions with Redis and scaled with RDS replication
- Built 1:N real-time group chat using WebSocket and Bull Queue for high traffic
- Designed and implemented a queueing system for reliable task processing
- Automated AWS IAM and Git environment setup
- Improved defect resolution efficiency by 40% using Jest-based tests
📦 Tech Stack: AWS, Nest.js, React, Redis, WebSocket, Bull Queue, PostgreSQL, Jest
HappyMade
Dev Team Lead2021.08 ~ 2022.01 · 6 months
- Delivered admin and user portals for an internal exchange service in PHP
- Integrated MySQL data and resolved production defects
📦 Tech Stack: PHP, MySQL, HTML, CSS, JavaScript
Han Communication
Developer2021.05 ~ 2021.08 · 4 months
- Maintained client websites and authored storyboards
- Delivered full-stack client sites on Cafe24
- https://hanleeon02.cafe24.com/main/
📦 Tech Stack: HTML, CSS, JavaScript
BeFle (BusinessPlus)
Corporate Researcher2020.09 ~ 2020.11 · 3 months
- Redeveloped the company website and delivered an admin panel
- Implemented PHP/MariaDB backend and JS/HTML/CSS3 frontend
- Built notice, gallery, and video modules
- Delivered end-to-end web publishing
- http://www.businessplus.co.kr/
📦 Tech Stack: PHP, MariaDB, HTML, CSS, JavaScript
Hanil Networks
Business Support Staff2017.01 ~ 2018.07 · 1 year 7 months
- Managed departmental costs, budgets, marketing, and planning
- Supported general affairs, accounting, document management, procurement, and ERP operations
📦 Tech Stack: ERP, MS Excel, Office
Skill Radar
Balanced strengths across product engineering, systems design, delivery, and AI integration.
88
Front-end
Next.js, React, UI systems
84
Back-end
Nest.js, APIs, data modeling
78
Cloud
AWS, CI/CD, observability
72
Systems
Kiosk and device integration
86
Collaboration
Cross-team execution with security focus
Hiring Snapshot
A concise, decision-ready profile.
Full-stack delivery across web, mobile, kiosk, and admin products.
Proven experience in platform design, real-time systems, and integrations.
Emphasis on reliable delivery, UX quality, and maintainable code.
Actively leverage AI to improve efficiency and quality.
Contact
Please reach out by email, or review my work on LinkedIn and GitHub.
