| name | data-safety |
| description | Data layer discipline — migrations, transactions, integrity, query safety. Load for any schema or data-access work. |
Skill: Data Safety
Datastore-agnostic — engine and ORM/driver come from memory-long §stack.
Non-negotiables
- Migrations are forward-only and reversible: every migration ships with a tested rollback; destructive migrations (drop/rename) use expand-contract (add new → migrate data → remove old, separate deploys)
- Transactions around invariants: multi-write operations that must succeed together are transactional — partial state is corruption
- No data deletion without explicit human sign-off — soft-delete by default; hard deletes are migrations with rollback plans
- Parameterized queries only — string-built queries are injection (security gate blocks)
Patterns
- N+1 vigilance: loops issuing queries → batch/join/preload per the stack's idiom
- Indexes follow queries: new query patterns on large tables come with index analysis in the report
- Constraints in the database, not only in app code — the DB is the last line of integrity (FKs, unique, checks)
- PII discipline: fields classified at schema time; PII never in logs; retention rules from memory-long §constraints
Verification
Migration up+down tested against realistic data volume · transaction boundaries reviewed on multi-write paths · query plans checked for new hot-path queries.
