Web Engineer · Tech Lead. 6+ years building backend systems for payment (PG), commerce (MSA), ticketing, and public SaaS. Reliable data flows and operations that don't break under load.
Notes on payments, settlement, infrastructure and running LLMs in production. Full archive at slecsblog.com ↗
6+ yrs of backend. Payment · Commerce · Ticketing · Public SaaS. Domain modeling · infrastructure · automation get most of my time.
Started as an application SW developer in 2020, working on public SaaS (nationwide education portals, a national R&D information portal) — that's where I learned the discipline of running large systems with strict compatibility constraints. Later moved to an easy-payment SaaS and a new PG construction, then an MSA-based e-commerce backend, and currently leading the ticketing payment & settlement platform at a ticket-commerce company.
Spring Boot · Java · MySQL · Redis · Linux/Docker as the daily stack. On the side, I do infrastructure / DevOps automation and build LLM-powered ops tooling I actually use day-to-day. I believe small details — indexes, lock ordering, transaction boundaries, error messages — make the largest difference.
Taste — fewer larger modules over many small ones, direct code over fancy abstractions, one more human review over yet another automated check.
19+ projects across 3 employers + 1 freelance period. Software development / application SW — backend · Tech Lead.
Leading backend for a Korean ticketing platform's payment, settlement, and partner-fee systems. Architecture, operational stability, and feature roadmap. Personally designing and implementing the core domain — multi-tier partner settlement, real-time balance & holding management, FIFO charge consumption, and per-method holding windows (virtual account / card) — while owning team code quality and release ops.
SaaS feature dev and advanced features for an easy-payment platform, new PG system construction, MSA-based integrated solution, and a scalable e-commerce platform backend.
Between two full-time roles, took freelance contracts via an SI firm. Solo backend work covering data ingest, integration, and cleansing for public-sector projects.
Multi-year maintenance and 1st/2nd/3rd-phase advanced development of nationwide education-portal application SW. Regional education-office platforms and public-agency websites — all with strict operational stability and backwards-compatibility constraints.
Mostly the things I use every day — I'd rather go deep with familiar tools than spread thin.
Categorized highlights from 19+ projects. Some details are NDA-protected.
SaaS feature dev and solution build for an easy-payment platform, full admin-page redesign, and a new solution-based PG system. Focus on payment-flow, settlement, and admin-ops stability.
Operator-centric e-commerce backend integrated with an MSA-based unified solution. Domain modeling for multi-channel / seller / settlement, ops UI, and deployment automation.
Payment, settlement, and partner-fee system for a Korean performance / ticket platform. Multi-tier partner settlement, real-time balance & holding, charge / payment / refund consistency. PENDING / CONFIRMED / CANCELLED state machine with FIFO charge consumption and per-method holding windows — virtual account (+2h) / card (+3d).
Multi-year maintenance and 1st/2nd/3rd phase advance development of the nationwide education-portal application SW, plus regional education-office platforms and public-agency website maintenance (full-time era). The national R&D portal construction was separate freelance work. Strict operational stability and compatibility-first development for public / government environments.
Solo build of the company site and team blog for a software studio I co-founded. Astro static blog (106+ posts), nginx + Cloudflare Flexible SSL on a cloud VM (Ubuntu 26.04), MySQL/Redis via Docker Compose. End-to-end ownership: infra, design, and content pipeline.
I'm not taking client work right now. I'm heads-down building our own products — hiring, freelance, outsourcing and consulting are on hold for a while. For anything else, feel free to drop a line.