Migration Safety Review

Use this skill as a safety gate before applying database migrations to real or production-like data.

Core Rule

Do not apply or approve a migration until its data, compatibility, locking, rollback, backup, and application-code risks have been reviewed.

Workflow

1. Identify migration scope:
   • file name, tables, columns, indexes, constraints, data transformations, models, APIs, frontend behavior, and whether existing data is modified
2. Classify risk level:
   • low, medium, high, or critical
3. Check destructive changes:
   • drops, deletes, truncates, irreversible transforms, unsafe renames, data type truncation, cascade deletes, enum removals
4. Check backward compatibility:
   • old code with new schema, new code with old schema, rolling deploys, background workers, mobile/old clients
5. Check existing data compatibility:
   • nulls, duplicates, orphan records, invalid enum values, type conversion, invalid dates/numbers
6. Check locking and downtime risk.
7. Review constraint safety and index strategy.
8. Check application code alignment:
   • models, validation, services, endpoints, frontend types, jobs, seeds, tests, docs
9. Decide if migration order should be split into staged rollout.
10. Review rollback plan and backup needs.
11. Review staging/dry-run and backfill strategy.
12. Pay extra attention to sensitive or financial data.
13. Produce a migration safety report with final recommendation.

Read references/migration-review-checklist.md for risk classification, pre-check queries, safe rollout patterns, and the report template.

Non-Negotiable Rules

• Do not approve destructive migrations without warning.
• Do not assume existing data is clean.
• Do not add NOT NULL, UNIQUE, or FOREIGN KEY constraints without checking existing data.
• Do not ignore application-code compatibility.
• Do not ignore mobile or old client compatibility when API fields change.
• Do not ignore rollback planning.
• Recommend backup for medium or higher risk migrations.
• Do not run destructive SQL without explicit approval.
• Do not perform large backfills without batching/resume considerations.
• Do not add cascade delete behavior casually.

Output Contract

When using this skill, provide:

1. Migration summary and risk level.
2. Tables/fields/indexes/constraints/data changes affected.
3. Destructive change check.
4. Backward compatibility and existing data compatibility.
5. Locking, constraint, and index review.
6. Application code alignment review.
7. Rollback, backup, and safe deployment recommendation.
8. Verification checklist and final recommendation.