Jiheung Jeong
SJ System · Founded March 10, 2023
I spent 16 years building enterprise systems. Now I use the same approach to help small businesses.
I have been building backend and AI services for 16 years. I have personally designed and implemented core systems such as the next-generation ERP and POS for Emart24, the Korea Forest Service's 'Supnadeul-e' public service for searching and booking recreational forests nationwide, Starbucks mobile enhancements, and, at a large enterprise, an internal AI help desk with RAG search and AI orchestration.
The conclusion I drew from that experience is simple: a system proves its value not by its scale but by the time it actually saves people. I confirmed this by deploying a company-wide AI service that improved the efficiency of handling work inquiries by more than 40% and cut repetitive work by 60%.
At SJ System, I bring that approach to small businesses. The person who consults with you, designs the system, builds it and operates it after launch is me. I never outsource or subcontract.
How I work
One person from planning to operation
The CEO personally handles requirements, design, development, deployment and post-launch operation. You never have to start over explaining things to a new contact.
Experience building large-scale systems
I built a B2B mall with KRW 300 billion in annual sales, core systems such as the next-generation ERP and POS for Emart24, and the Korea Forest Service's 'Supnadeul-e' public service, which lets anyone search and book some 140 recreational forests nationwide. I built big before I learned to build small.
Hands-on experience applying AI
I designed and implemented an internal AI help desk and rolled it out company-wide. I work directly with RAG document search, vector databases and conversational AI orchestration. These are technologies I have operated, not buzzwords.
Payments built in-house
I developed StayPay, a payment and settlement system for lodging properties, completed mail-order business registration, and it is processing real payments. Payments are something I operate, not just something I've integrated.
Contact goes straight to the CEO
There is no sales rep in between. Inquiries, incidents and additional requests all go directly to the CEO's number.
Key projects
AI · Task Automation
Projects that moved repetitive responses and processing from people to AI and automation.
- Built and rolled out an internal AI help desk company-wide at a large enterprise — AI orchestration combining RAG document search, vector DB, conversational AI and image generation. Improved work-inquiry handling efficiency by more than 40% and cut repetitive work by 60%
- Launched an infrastructure portal in two months — sole full-stack development covering planning, design, frontend, backend, DB and external integrations. The entire process was run with Claude Code, applying harness and loop engineering
- Brought an internal portal in-house — unifying cafeteria ordering, meeting room booking (with calendar integration) and asset/supply rentals
- Built and stabilized an attendance management system — clock-in/out, leave, family-event and leave-of-absence requests, with messenger chatbot and calendar integration
Public Sector · Large-Scale Systems
Built and operated systems that had to handle millions of users and hundreds of billions of won in transactions.
- Built the Korea Forest Service's 'Supnadeul-e' big-data-based integrated forest recreation platform — a public service that lets anyone search and book some 140 recreational forests nationwide
- Built the next-generation ERP and POS for Emart24 — stable operation of promotion, sales and customer data
- Built the next-generation ERP, smart office, 3PL logistics system and B2B mall for Emart Everyday — the B2B mall reached KRW 300 billion in annual sales; integrated with CJ Logistics
- Starbucks mobile enhancements — improved sign-up UX, implemented deep links, introduced Firebase Analytics
- Shinsegae Department Store system operations — Java-based development and query tuning
- In-house mobile office development — product lookup, ordering, inventory and sales management
Core skills
- Java · Spring Boot
- Python
- Next.js · TypeScript
- AI orchestration · RAG
- Vector DB
- AWS · Google Cloud
- MySQL · BigQuery
- Docker · CI/CD
Education
- B.S. in Information & Communication Engineering, Dongguk University
- M.S. in Information & Communication Engineering, Dongguk University
* Selected projects from 16 years of work. Employer names are not disclosed; details can be shared during a consultation.
Things we built ourselves
STAYTOQ
An AI chatbot SaaS for lodging businesses — planned, built and operated entirely in-house, and running live for clients.
Learn more →Goeunheuk website
Planning, design and development of a website for a red clay manufacturer, plus a STAYTOQ chatbot.
See the case →StayPay
Our own payment system that lets lodgings take bookings and payments directly — rooms and day-use products, real-time booking, cancellation and refund policies, and booking lookup. Registered as a mail-order business and processing real payments.
View checkout page ↗Yangju JamJam Glamping website
Planned and built the website of a glamping site near Seoul — rooms, facilities, nearby attractions and the booking flow — with a STAYTOQ chatbot on top.
Visit site ↗CallPop
A local restaurant discovery platform, being developed as a hybrid web app for JudoSystems.
See the case →We give our customers their time back.
AI takes on the repetitive work, so people can spend their time on what only people can do.
About SJ System →