A multi-tenant point-of-sale platform
A point-of-sale product for small shops — a checkout app that keeps selling offline, an owner dashboard, a platform-admin console and subscription billing — built and deployed end to end.
- Problem
- Small shops need to ring up sales, track stock and close shifts on whatever device is at the counter, and they cannot stop selling when the connection drops. Each shop's data must stay isolated on one shared backend, and the platform has to bill shops for their plans.
- Contribution
- Sole developer. I designed and built the Angular checkout and admin apps, the NestJS API, the PostgreSQL schema, the realtime and offline sync, the billing and payment integrations, the CI pipeline and the EC2 deployment.
- Approach
- An Nx monorepo holds three apps: an Angular point-of-sale web app with a service worker and IndexedDB, an Angular platform-admin console, and a NestJS API on Fastify with Prisma over PostgreSQL. Tenancy is enforced in middleware that derives the shop from the access token, while the platform-admin plane uses a separate secret and never gets a shop context. Redis backs BullMQ jobs for work such as invoice renewal. Sales events reach open devices over WebSockets. Production runs on EC2 behind nginx with PM2, TLS from Let's Encrypt, and PostgreSQL on RDS.
- Outcome
- The product covers checkout, returns, inventory reservation, shelf-life lots, shifts, sales analytics, receipts, store settings, staff, VietQR and SePay payments, plan subscriptions with auto-renewal, and a platform-admin console. CI lints, tests and builds affected projects, enforces a bundle budget, scans for CVEs with Trivy and runs Playwright end-to-end tests.