About

I build the whole thing —
not just the website.

I'm Sihyeon Jegal, the developer behind sihyeonzon. I design, build, and run production software for a living — including my own SaaS product with real, paying users — which is why the sites I build for clients are engineered to actually bring business in, not just look good.

150K+
SEO pages generated
1
Developer, full ownership
5+
Years building web products
UK
Based studio
Sihyeon Jegal, founder and full-stack developer
Why it matters

Most agencies design pages. I ship products.

Alongside client work, I founded and independently built LeadBoba, a B2B lead generation platform, from the first line of code to a live product with paying users. I own the entire stack myself: product design, frontend, backend architecture, cloud infrastructure, and day-to-day operations.

That includes a large-scale data extraction system, rotating proxy infrastructure for reliable web-scale crawling, AI-powered outreach generation, and a programmatic SEO engine that has generated over 150,000 indexed pages targeting real search demand across cities and industries. It's the same automation and SEO thinking I bring into every client site — built to be found, not just built to look right.

Read the LeadBoba case study ↗
LeadBoba product dashboard screenshot
Toolkit

What I actually build with.

Frontend

  • React
  • Next.js
  • TailwindCSS
  • SCSS

Backend

  • Node.js
  • Express
  • REST APIs
  • JWT / OAuth

Data

  • MySQL
  • MongoDB
  • Redis

Infrastructure

  • AWS (EC2, ECS, ECR, ALB, S3, RDS)
  • Docker
  • GitHub Actions CI/CD
  • Nginx

Growth

  • Technical SEO
  • Programmatic SEO
  • Automated outreach
  • Data pipelines
Background

How I got here.

01

Founder & Full-Stack Developer — LeadBoba

Oct 2025 — Present, United Kingdom

Designed, built, and deployed a B2B lead generation SaaS end to end — product, frontend, backend, infrastructure, and operations, as the sole developer.

02

Web Developer — Client Projects

2024 — 2025

Built and shipped production websites for clinics and small businesses, handling everything from layout and frontend build to deployment and go-live.

03

Naval Architecture & Marine Engineering

University of Ulsan, Graduated 2025

An engineering background that carried over directly into how I approach software: structured problem-solving, systems thinking, and a bias toward things that actually work in production.

Work with me directly

No account managers.
Just the person building it.

Start a project