# Migration Planning

> Move data or systems without a night-of surprise. Dual-write, backfill, cutover, rollback. Use when the user asks to migration plan.

- Skill: `delzarsolutionsllc/migration-planning` (Agent Skill)
- Install (CLI): `npx skillmds@latest add delzarsolutionsllc/migration-planning`
- Raw SKILL.md: https://api.skillmd.com/api/skills/delzarsolutionsllc/migration-planning/raw
- Safety review: pending
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Coding & Dev Tools
- Author: delzarsolutionsllc (https://skillmd.com/u/delzarsolutionsllc)
- Updated: 2026-09-21
- Page: https://skillmd.com/skills/delzarsolutionsllc/migration-planning

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# Migration Planning

A migration is a sequence of reversible steps, not a weekend.

## Plan shape
1. **Why** — the invariant the old system cannot keep.
2. **Inventory** — data, callers, jobs, SLAs, rollback windows.
3. **Strategy** — expand/contract, dual-write, shadow-read, or one-time copy. Pick one and say why the others lost.
4. **Steps** — each step is deployable, observable, and reversible on its own.
5. **Backfill** — batch size, idempotency, how you know it finished.
6. **Cutover** — the flag, the watch, the abort.
7. **Cleanup** — when the old path dies, and who turns it off.
8. **Risks** — the two ways this pages the on-call.

Do not schedule "migrate everything" as step 1. Do not skip the abort criterion.