Software shaped around a real business.

I developed La Central to bring the operations of a grocery store in Costa Rica into a system tailored to how it works. I built the interface, backend, database and local deployment, together with backup and recovery tools.

La Central point of sale with a weighted product and automatic egg carton pricing — Point of sale · Demonstration data. Weighted products and pack pricing.

My contribution: Complete development: interface, backend, data, deployment and backups.
Status: Development completed · Awaiting installation
Year: 2026

The starting point

Every sale affects more than inventory.

A checkout can combine weighted products, units, packs, cash and customer credit. It affects stock, cash and the customer’s balance while another cashier works with the same data. Those operations need to remain consistent through retries and concurrent actions.

Built for the store

One local network. One shared source of data.

The main PC serves the application and holds the database. Registers work in a browser and receive stock updates through Socket.IO.

MAIN PC

NestJS + PostgreSQL

Docker Compose · Nginx

LOCAL NETWORK / LAN

Browser

Example of a two-register installation. The main PC and network must remain available.

Decisions that shape the product

Multiple registers, one operation

A main PC runs the server and database. Other registers connect through a browser on the local network. Daily operation works without Internet as long as the main PC and network remain available.

Retry without duplicating

If a checkout confirmation is lost, the interface retains the operation key. A retry with the same data can return the sale already recorded. Transactions coordinate the sale, inventory and cash record.

Sell the way the store works

Individual units and cartons share inventory; weighted products support gram entry. Pack prices are applied to the total, and sales retain historical descriptions, prices and conversion factors.

Restock with information and judgment

Suggestions consider net sales, minimum stock, available inventory and outstanding orders from every supplier. Users can accept part of a proposal and edit quantities and costs before creating an order.

Prepare for recovery too

Deployment includes backups, restore checks in an independent container and integrity checks. Partial deliveries, returns and supplier credits maintain their own balances and history.

Supplier order in La Central with products and costs — Purchasing · Preparing a supplier order with demonstration data.

Implementation and verification

documented tests

receipt formats verified as PDFs

LAN

shared installation on the store network

September 14–16, 2026 verification: 15 unit tests, 33 integration tests and 5 browser journeys passed. Errors found during several days of simulated operation were corrected and the flows checked again. Backup recovery was also documented.

Technologies

React
TypeScript
NestJS
Prisma
PostgreSQL
Docker

Current scope

Development completed and validated in testing. Launch awaits purchase and configuration of the store’s equipment, including the printer. Payment methods are recorded; cards and SINPE are not processed. Receipts have no Hacienda integration. Screenshots use demonstration data.

The work covers the sale a cashier sees and the data, exceptions and recovery that support the operation.

Next project

Selvática

Let’s build something together.

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