History and Soft Deletion

Decide deliberately whether you need history. Most applications need it somewhere and model it nowhere, then discover the need after the data is gone.

The question: when this value changes, does anyone ever need to know what it was before? A price, an address, a permission, an order status: usually yes. A display name: usually no.

Soft deletion is a trade, not a free win. A deleted_at column keeps the row and marks it gone.

What it buys: recovery, audit, and referential integrity that does not break.

What it costs: every single query must now remember to exclude deleted rows, and the one that forgets is a data leak. Unique constraints stop working as intended, because a deleted row still occupies the name. And 'delete my data' from a user is not satisfied by a flag.