Startup BuildFlagship

Fjord Edu
Built a college-admissions academy's booking, payment, student workflow, and internal operations platform — handling over KRW 300 million in payments in a single day without downtime.
PersonalDuration 8 moContribution 100%2025-05 → 2025-12
★Key Metric: First-come booking engine · ~2,000 concurrent bookings serialized
◆User Scale: Over KRW 300 million in payments in a single day · all opening traffic handled with zero incidents
Engineering Role
FullstackEnd-to-EndInfra

Startup Build
Fjord Edu
AI
#Web#Frontend#Backend#Product
Overview
I built the booking, payment, student workflow, and internal operations platform for a college-admissions consulting academy from May through the end of 2025. It combines consultation booking, payment, pre-surveys, document uploads, and administrator assignment, with a FOR UPDATE SKIP LOCKED + Optimistic Locking booking engine and Toss PG handling over KRW 300 million in payments in a single day without downtime.
My Work
- ▸Owned the full lifecycle across planning · UX · design · full-stack development · deployment · operations
- ▸Serialized ~2,000 concurrent bookings with FOR UPDATE SKIP LOCKED + Optimistic Locking + RPC
- ▸Integrated Toss PG confirm, recovery, whitelist revocation, and 10-minute hold expiry
- ▸Built one Google · Kakao OAuth callback for identity linking and inactive-account blocking
- ▸Applied Supabase RLS, security definer hardening, and 100+ SQL migrations
- ▸Built admin-editable cms_pages, block visibility, SEO meta, banners, menus, and popups
Features
- First-come slot lookup/booking/payment flow (handling ~2,000 concurrent users)
- Toss Payments approval/refund + payment recovery / automatic whitelist revocation
- Google · Kakao · Email login + account linking on My Page
- Pre-survey questionnaire + administrator CSV export
- Document submission upload (PDF/JPG/PNG/HWP/ZIP · 100MB)
- Page-builder CMS for home, booking, notices, and regular-admission pages
Highlights
- Built May–Dec 2025 · maintenance and operations since
- First-come booking engine (FOR UPDATE SKIP LOCKED + Optimistic Locking + RPC)
- Handled all opening traffic · over KRW 300 million in payments in a single day with zero incidents
- Toss Payments PG approval · refund · pg_cron 10-minute hold auto-expiry
- CMS — page builder · block visibility · banners · menus · popups · per-page SEO meta
Timeline
2025-05 → 2025-12
Role: Planning · design · full-stack development · deployment · maintenance operations
Contribution: 100%
Collaboration: Personal
Tech Stack
</>Next.js · Supabase RLS · Toss PG · first-come booking engine
Next.js 16React 19TypeScriptTailwind CSSSupabasePostgreSQL (RLS · FOR UPDATE SKIP LOCKED · pg_cron)Toss PaymentsRechartsPlotly.jsTiptapVercel