Hi, I'm Sang.

Built at Citi to catch and escalate payment control failures across 52 global applications — processing ~25M records monthly and validating roughly $1.5 trillion in payment value every cycle. Designed and built from scratch as the sole developer: a config-driven Python platform running 4 pipeline types — Threshold Validation, Duplicate Detection, Dual Blind Rekey, and GPOC executive reporting — each with its own business rules per application. Reduced ~90% of manual effort per monthly cycle, saving 150+ hours. The codebase is internal to Citi — the architecture and outcomes are mine to discuss.

Internal tool — codebase confidential per Citi policy

A live financial data monitoring service built and deployed on AWS — ingesting U.S. economic indicators daily via the FRED API, detecting anomalies, and serving alerts through a secured FastAPI layer backed by PostgreSQL. Built specifically to close real gaps: AWS infrastructure provisioned with Terraform so the entire server can be rebuilt from scratch in under 2 minutes, GitHub Actions CI/CD so every push runs tests before touching production, and pytest coverage maintained across 3 months of active development. Completed a pre-launch security audit — 6 vulnerabilities identified and resolved before the first public deployment.

Built from scratch as a first-time parent who couldn't find one app that did everything. ThriveKid is a deployed full-stack PWA — 12 feature modules, JWT authentication with refresh token rotation, a timezone-aware recurring event engine, and WHO percentile growth charts. Clean Architecture across a 3-layer .NET 8 backend, React 19 TypeScript frontend deployed on Vercel, Docker multi-stage builds, and GitHub Actions CI. Went through two full mentor code reviews with a senior engineer — 25+ issues identified, all resolved, including a 13-issue security audit conducted before public launch. The project that taught me what good engineering actually looks like.