Migrationsauslieferung prüfen

Migration & Rollout Review

Use this skill when reviewing changes that include database schema migrations, data transformations, storage format updates, or environment configuration changes.

Workflow

1. Verify safety against existing production data:
   • Never evaluate a migration only against an empty test database. Check what happens when tables already contain existing rows:
     • Adding a NOT NULL column without a safe DEFAULT or backfill step will fail on non-empty tables.
     • Adding a UNIQUE constraint or narrowing a column type will fail if legacy rows contain duplicates or out-of-range values.
     • Dropping or renaming a column/table while code or views still reference it causes immediate runtime errors.
2. Check version coexistence and rollout order (Expand & Contract):
   • Verify whether the migration and code change can deploy safely:
     • Does old code break if the migration runs seconds before the new application process starts?
     • Does new code handle legacy rows created before the migration (e.g., nullable fields, older JSON schema versions, missing metadata)?
3. Audit performance, locking, and rollback safety:
   • Check whether missing indexes on new foreign keys or filter columns will cause full-table scans as data grows.
   • Flag migrations that rewrite or lock large tables synchronously during request handling without batching.
   • Verify whether the change is reversible (or has a documented forward-fix path) if a rollback is required after deployment.
   • Coordinate deep database engine specifics with the database and DevOps specialists.