S.M.I.L.E: booking and payments for a dental clinic network

Practice management for a multi-clinic dental network.

Role: Owner of booking, payments and identity
Context: Capstone, FPT University
When: 2026

A seeded patient books a slot at the Hà Nội clinic and pays through the VNPay mock, recorded on the local stack at twice the speed.

4NestJS services behind one gateway
5PostgreSQL databases, one per bounded context
145test files across the NestJS services and the front end

Overview

A practice management platform for a multi-clinic dental network: four NestJS services on Bun, one of them the API gateway, five PostgreSQL databases, Redis and a Next.js front end. I owned the parts where a bug costs a patient money or a seat.

Booking: two patients cannot claim the same doctor's slot, even with simultaneous requests, because the check happens in the database, not in application code. Availability updates in the UI in real time.

Payments: VNPay by QR or redirect, callback handling, refunds with an approval workflow, and payment history in the service's own database. A Redis-backed idempotency key means a retried request never charges twice; the VNPay callback is signature-verified and replay-guarded.

Identity: a standalone Python OCR service reads Vietnamese citizen ID cards, and the IAM service uses it to gate who may book. I also shipped a LangGraph booking assistant with Qdrant retrieval for clinic policy questions.

Retries and double bookings, simulated

Idempotency key in Redis

0 payments created

0 marked paid

A simulation of the rules the services enforce, not the live system. Keys and amounts are made up.

Built with

NestJS
Bun
TypeORM
PostgreSQL
Redis
VNPay
Next.js
LangGraph
Qdrant
Python OCR