ShopGuard

Small retailers here tend to be caught between two bad options. A cash register handles the sale but tells the owner nothing. An enterprise retail suite tells them everything but needs a consultant to set up and a licence per terminal.

ShopGuard sits in between. It is one deployment that can run many shops, with the tenant boundary enforced in a single place in the code rather than scattered through every query — which is what makes it safe to put two competing shops on the same instance.

The system splits into three portals. The platform console is for onboarding a new shop and seeing across the network. The shop admin covers inventory, categories, cashiers, sales, reports and an audit log of who changed what. The till is deliberately the simplest surface of the three: a cashier signs in with a PIN, scans, and takes payment.

The till is also the part most carefully built. It is phone-shaped, with the cart as a bottom sheet rather than a sidebar, because a lot of these shops hand a phone to whoever is at the counter rather than buying a dedicated terminal. Receipts print. The interface is designed to be learnable in about ten minutes, without training.

Under it: Next.js on the App Router, Prisma against PostgreSQL, NextAuth for the admin logins and a separate signed-JWT scheme for cashier PINs — because a cashier session and an owner session should never be the same kind of credential. Light and dark themes are both first-class, since a till sits under fluorescent light and an office does not.