Building a Scalable Inventory System with Next.js and PostgreSQL

A manufacturing client came to us with a familiar problem: their inventory was managed across three locations using a shared spreadsheet. Stock counts were wrong, reorder triggers were missed, and the operations team spent hours every week reconciling data manually.

We built a custom inventory management system using Next.js for the frontend and PostgreSQL for the database, with Redis handling real-time stock updates across locations.

The core of the system is a transaction log — every stock movement (receipt, dispatch, adjustment) is recorded as an immutable event. Current stock levels are derived from this log, which means you always have a full audit trail and can reconstruct the state at any point in time.

For the multi-location sync, we used PostgreSQL's LISTEN/NOTIFY combined with a lightweight WebSocket layer. When stock changes at one location, all connected clients see the update within seconds — no polling, no stale data.

Automated reordering was the feature the client cared most about. We built a rules engine where each SKU has configurable reorder points and quantities. When stock drops below the threshold, the system generates a purchase order draft and notifies the procurement team. They review and approve — the system doesn't place orders autonomously, which was an explicit requirement.

The result: 40% faster processing, 99.9% uptime across six months of production use, and the operations team reclaimed roughly 12 hours per week that was previously spent on manual reconciliation.

The stack was deliberately boring: Next.js, PostgreSQL, Redis, deployed on a VPS with Docker. No microservices, no event streaming platform, no Kubernetes. The client needed something reliable and maintainable by a small team — not a distributed systems showcase.