POS — the sales screen on a laptop and the mitpvonline.com landing page on a phone

Custom Development · 2026

POS — Point of Sale for SMEs

POS — a web-based, scalable, multi-device point of sale for small and medium businesses

Case study

A web POS, scalable and multi-device, built to grow with the shop

The challenge

Small businesses that open the till every day face an awkward choice: legacy cash registers that don't talk to their accounting, closed POS software licensed per terminal and per sector, or spreadsheets and loose apps held together with tape. The result is manual till closings, discrepancies that are hard to audit, stock that is always out of date and no real visibility of the business when the accountant arrives. The challenge was to build our own professional, scalable POS that replaces the till, stock control, the customer and supplier directory and sales reports in one go — usable from tablet, phone and desktop, installable as an app, able to run a small shop today and a multi-sector chain tomorrow.

Our solution

We designed and built a complete web POS on a modern stack (Angular 20, NestJS, PostgreSQL, Docker), with a modular architecture that covers sales, till, inventory, customers, suppliers, users, auditing and settings in a single application. The sales terminal is made for touch: a product grid with images, search by name or SKU, a native barcode reader on phones and tablets (Android via ML Kit, iOS via zbar-wasm behind the same standard API), category filters and a cart with discounts. Checkout opens a dialog with the payment methods the business has set up (cash, card, Bizum, any others) and issues an 80 mm PDF receipt that can be printed, downloaded or sent by WhatsApp straight from the success screen. Till management is the real thing: opening with a float, deposits and withdrawals with a reason, cash count and closing with the discrepancy calculated, all with real-time updates over SSE so the manager sees movements on their screen as they happen. The history can be exported to CSV, broken down by payment method and VAT. The admin panel includes a dashboard with daily, weekly and monthly sales, minimum-stock alerts and top products; inventory with movement history, adjustments with structured reasons (receipt, shrinkage, theft, gift, return to supplier…) and automatic purchase orders grouped by supplier when stock falls below the configured minimum; sales history with date and payment-method filters, voids and partial returns; a customer directory with full purchase history and the detail of each sale; and user management with three predefined roles (admin, manager, cashier) and 17 granular permissions. Security is designed for a real shop: two-step login (email and password for identity, numeric PIN to open the till), JWT with rotating refresh tokens in an HttpOnly cookie, automatic lock on inactivity (5 minutes idle or 30 seconds with the screen off) that only unlocks with the PIN, rate limiting on login, bcrypt with 12 rounds, AES-256-GCM encryption of personal data (ID number, email, phone) with an HMAC index to search without decrypting, a global audit log of every change with credentials sanitised, and Helmet headers in production. It is an installable PWA with a service worker, offline asset cache, manifest and icons, and session persistence when the app opens: staff install the POS on their tablet, sign in once and the next session starts without typing passwords again. It is also multi-currency (EUR, USD, GBP, MXN, ARS) and multi-language (Spanish, English) with live switching. Full deployment on Docker Compose on a VPS with Plesk and Let's Encrypt, automatic daily PostgreSQL backups kept for 14 days, and CI/CD with GitHub Actions: every push to main triggers a build and deployment with a smoke test. It is live at tpv.avilaweb.es.

POS — Point of Sale for SMEs — full desktop screenshot

POS — Point of Sale for SMEs — full mobile screenshot

03 / 12

A sales terminal built for a real shop

Product grid with images, search by name or SKU, category filters and a side cart on desktop or a drawer on mobile. Made for touch and ready to sell from the first tap.

04 / 12

Checkout in one step

Payment dialog with the methods the business has set up. It creates the sale, generates the PDF receipt and opens the success screen with download, print and WhatsApp.

05 / 12

Receipt by WhatsApp from the success screen

Web Share API with the PDF attached and a wa.me fallback. The customer gets the receipt on their phone without typing emails or installing anything.

06 / 12

Cashier panel

The shift at a glance: sales and takings since the till opened, low-stock products and the month's best sellers. Opening, deposits, withdrawals, cash count and closing are recorded in real time for the manager.

07 / 12

Inventory with real history

Every stock movement is recorded with a structured reason (receipt, shrinkage, theft, gift, return to supplier…) and an optional note. The reason sets the direction: «shrinkage» can only subtract, «receipt» can only add.

08 / 12

Sales history with auditing

Filters by date and payment method, full detail of each sale, voids and partial returns. CSV export of up to 10,000 sales with the active filters.

09 / 12

The customer and their history, in one view

Customer record with personal data encrypted (AES-256-GCM) and HMAC search. Full purchase history with the detail of each sale without leaving the modal.

10 / 12

Three roles, 17 permissions, a clear matrix

Admin, manager and cashier as a base, with 17 granular permissions editable per user. PIN to open the till, password for identity. Global PermissionsGuard on the backend.

11 / 12

Auto-lock on inactivity

After 5 minutes without touching the screen, or 30 seconds with the screen off, the POS locks. Unlock with the PIN, without signing out or losing the cart in progress.

12 / 12

Audit log of everything that changes

Every POST, PATCH and DELETE is recorded with user, route, status code and duration. Credentials are sanitised before saving. Filters by route, user and date range.

Project specs

Client

Producto interno HazmeWeb

Year

2026

Site type

saas-application

Technologies

Angular 20 (PWA), NestJS 11, TypeScript, PostgreSQL 17, Prisma 7, Tailwind CSS 4, Transloco i18n, Docker Compose, Nginx, GitHub Actions

Builder

Desarrollo a medida

Languages

Español, Inglés

Integrations

Native barcode reader (ML Kit Android / zbar-wasm iOS), PDF receipts (jsPDF), receipts via WhatsApp (Web Share API + wa.me), CSV export, Server-Sent Events for real time, Let's Encrypt + Plesk, GitHub Actions CI/CD

Features

Multi-device POS terminal (tablet, phone, desktop)Native barcode reader on Android and iOSTwo-step login (email + PIN) with three roles and 17 permissionsTill management with opening, cash count and closing, in real time (SSE)80 mm PDF receipts sent by WhatsApp from the same screenInventory with minimum stock, movement history and structured reasonsAutomatic purchase orders grouped by supplierSales history with filters, voids and partial returnsCustomer directory with purchase history and sale detailsDashboard with metrics, stock alerts and top productsGlobal audit log of changes with sanitised credentialsAutomatic lock on inactivity with PIN unlockSession persistence and rotating refresh tokens in an HttpOnly cookieAES-256-GCM encryption of personal data (GDPR)Multi-currency (EUR, USD, GBP, MXN, ARS) and multi-language (ES, EN)Installable PWA with offline cacheCSV export of sales, inventory and tillDocker deployment with CI/CD and automatic backups

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POS — Point of Sale for SMEs