# Migration Strategy

> Plan large-scale migrations from old systems to new architectures. Use when modernizing legacy systems or upgrading infrastructure.

- Skill: `sethdford/migration-strategy` (Agent Skill)
- Install (CLI): `npx skillmds@latest add sethdford/migration-strategy`
- Raw SKILL.md: https://api.skillmd.com/api/skills/sethdford/migration-strategy/raw
- Safety review: pending
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Coding & Dev Tools
- Author: sethdford (https://skillmd.com/u/sethdford)
- Updated: 2026-09-17
- Page: https://skillmd.com/skills/sethdford/migration-strategy

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# Migration Strategy

Plan phased migrations that minimize risk and disruption while delivering value incrementally.

## Instructions

1. **Assess Current State**: What's working? What's broken?
2. **Define Target State**: New architecture vision
3. **Identify Seams**: Where can you break the system into phases?
4. **Plan Phases**: Each phase delivers value; takes weeks to months
5. **Risk Mitigation**: Parallel running, feature flags, rollback plans
6. **Success Metrics**: How do we measure success of each phase?

## Anti-Patterns

- **Big Bang Rewrite**: Replace everything at once. Result: chaos and failure. **Guard**: Incremental, staged migration.
- **No Parallel Running**: Migrate directly without validation. **Guard**: Run old and new in parallel, validate.

## Further Reading

- _Strangler Fig Pattern_ — incremental replacement
- _Monolith to Microservices_ by Sam Newman