The Problem: One Shared Database

The previous lesson stated the rule: each service owns its own data store. This lesson shows why teams adopt that rule. We will follow one e-commerce system through a normal week. Three parts share one database: OrderService, InventoryService, and a nightly reporting job. Each one reads and writes the same tables.

A Shared Database Looks Convenient

At first, the shared database looks like the easy choice. OrderService writes a row to the orders table. InventoryService reads that row and lowers the stock count in the inventory table