[Terr_]

So just tangentially-related to foreign-key usage?

Here's one: Even if it looks convenient, ON DELETE CASCADE is often not what you want. Customers usually need something much more complicated, so you'll be writing external remove-these-before-those loops and steps anyway.

For example, a platform will never really want to wipe out the entire subgraph of records for a Customer or Product. Instead they'll want to "temporarily deactivate" the account, or at most "mark as permanently disabled, erase some sensitive or bulky information, and insert some audit/reason medatata."

Exceptions might be where the related-tables are purely a technical implementation detail, and don't represent domain objects the business thinks or cares about.