# Database Migrations

> Plan additive, zero-downtime schema migrations with rollout, backfill, and rollback awareness. Use when renaming columns, backfilling data, or shipping risky database changes.

- Skill: `hoangnguyen0403/database-migrations` (Agent Skill, multi-file: 3 files)
- Install (CLI): `npx skillmds@latest add hoangnguyen0403/database-migrations`
- Raw SKILL.md: https://api.skillmd.com/api/skills/hoangnguyen0403/database-migrations/raw
- Safety review: pending (external: skill-scanner PASS, skillspector PASS)
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Coding & Dev Tools
- Author: HoangNguyen0403 (https://skillmd.com/u/hoangnguyen0403)
- Updated: 2026-09-09
- Page: https://skillmd.com/skills/hoangnguyen0403/database-migrations

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# 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.

## Anti-Patterns

- **No destructive one-shot rename**: expand and migrate first.
- **No hidden backfill**: long data moves need explicit plan and observability.
- **No app deploy coupling by accident**: schema and code rollout order must be clear.

## References

- [Framework Map](../references/framework-map.md)
- [Migration Safety Checklist](references/migration-safety-checklist.md)