Database Migrations

Priority: P0 (CRITICAL)

Use expand -> backfill -> contract for risky changes.

Rules

• Ship additive schema first.
• Backfill with resumable logic and visibility.
• Flip reads/writes only after new shape is populated.
• Drop old columns or indexes in a later safe step.

Verify

• Migration can run without taking the app offline.
• Backfill ownership, batching, and monitoring are defined.
• Rollback or pause strategy exists.
• Old and new code paths can coexist during rollout.