Supermarket Loyalty App

The chain’s loyalty scheme ran on plastic cards and paper statements, and it knew almost nothing about its shoppers. Shoppers forgot or lost their cards, every offer went out in the same weekly leaflet, and the marketing team had little idea which offers worked or who its most loyal customers were.

Any replacement had to work with the tills already in every store, keep the checkout moving on a busy Saturday, and treat customer data with the care the GDPR demands.

We spent time at the tills and the customer service desks, and spoke with regular shoppers of all ages.

• Families shop as a household. Two adults with two cards were each collecting half the points they deserved.
• Leaflet offers felt random. Shoppers who never bought meat were offered meat every week.
• Older shoppers wanted it simple: a card that works, without having to learn a new app.
• Cashiers feared anything that slowed the queue.

The app’s digital loyalty card is a barcode that cashiers scan at the existing tills, exactly like the plastic card. The till sends the basket to the loyalty system, which adds the points and applies the shopper’s activated offers before the receipt prints.

If the network drops, the till keeps working: points and offers are queued and added as soon as the connection returns. Shoppers who don’t want the app can add the card to Apple Wallet or Google Wallet, or keep their plastic card.

Existing members moved across by entering their old card number, and their points came with them. A household account can hold several cards, with every card adding to one shared balance.

Offers now follow what each household actually buys. Shoppers are grouped by how they shop, such as a weekly big shop, frequent top-ups, fresh food, family essentials or own-brand value, and the marketing team builds offers for each group:

• money off products a shopper buys regularly;
• extra points on categories they are starting to explore;
• spend-and-get offers for the weekly shop.

Shoppers activate the offers they want in the app before they shop, and activated offers apply automatically at the till.

Many grocery offers are paid for by brands rather than the retailer. The marketing console lets the team create supplier-funded offers alongside its own, and records every redemption, so each supplier can be reported to and billed accurately.

In the same console, the team builds shopper groups and offers, schedules them, and sees which offers were activated and used, store by store.

After every shop, a digital receipt appears in the app with the points earned and the savings made. Shoppers see their points balance, their household’s cards and their activated offers in one place, and weekly offers arrive as a notification if they choose to receive one.

Privacy choices sit in plain view. Shoppers decide whether to receive marketing and can change their mind at any time. They can download or delete their data from the app. Only the data the loyalty programme needs is collected, it is kept only as long as needed, and access is limited to the staff who need it.

The app is built in Flutter for Android and iPhone. A NestJS API on PostgreSQL runs the loyalty system, with Redis keeping till lookups fast. A till integration layer connects to the chain’s existing point-of-sale system. Shopper groups are built in BigQuery, notifications go out through Firebase Cloud Messaging, wallet cards are issued for Apple Wallet and Google Wallet, and everything runs on Google Cloud in Europe.

Two stores piloted the app for a month, with cashiers trained beforehand and staff at the customer service desks helping shoppers move their cards across. Every store then switched, with signs at the entrance and at every till. Plastic cards still work, so nobody was left behind.

Shoppers carry their loyalty card on their phone or in their wallet, collect points as a household, and get offers that fit what they actually buy. The checkout keeps moving, the marketing team sees which offers work, store by store, and supplier-funded deals are reported accurately.