When you’d need it

A product spec says what users can do, but engineering needs to know how the data hangs together. An ERD turns a product story into tables and relationships before implementation starts.

Key decisions

• Core entities are shown as tables with primary and foreign keys so engineering can review the model.
• Relationships are labeled where the business meaning matters, such as a customer placing an order.
• The example stays small enough to inspect, which is more useful than a giant schema wall at the planning stage.

When to copy vs. adapt

Copy this for early database planning, docs, or handoff. Expand it when you have real fields, cardinality rules, or integration tables to add.