How to Prevent Duplicate POS Sales from Skewing Inventory with Python and SQLite
A point-of-sale register sells two pairs of boots. The inventory worker deducts two units and commits the change. Then the worker crashes before it acknowledges the message. When the worker restarts, the broker delivers the same sale again. If the handler runs the same inventory update a second time, stock drops from eight units to six even though the register sold only two. In this tutorial,…
Duplicate sales at a point-of-sale register can cause inventory levels to drop incorrectly. To prevent this, give each sale a unique event ID. When the worker crashes after processing a sale, the same message can be delivered again. If the handler doesn't handle this properly, inventory will be over-stated.
First, create a Python program using SQLite. This will handle the sales and check if a sale has already been processed. Run the program and perform a sale, then try running it again with the same event ID. The second run should be ignored, keeping inventory correct.
Also, test what happens if a sale references a SKU that doesn't exist, or would make inventory negative. The program should handle these errors. With the event ID system, duplicate sales are prevented, ensuring inventory remains accurate.
Written by urgent.news from Dev.to's reporting — not their text. Machine-written — may contain errors; check the original before relying on it.
