Migration Patterns
Strangler Fig / Branch by Abstraction / Parallel Run pattern definitions, implementation steps, and code examples → reference/migration-strategies.md.
Migration Checklist
Before migration:
- Document current behavior (tests as documentation)
- Identify all integration points
- Create feature flag for gradual rollout
- Define rollback procedure
- Set up monitoring/alerting for the new system
During migration:
- Migrate in small, reversible increments
- Run parallel comparison where possible
- Monitor error rates and performance
- Keep old code path available for rollback
After migration:
- Remove feature flags and old code paths
- Update documentation
- Archive or delete legacy code
- Retrospective: document lessons learned
Risk Assessment Matrix
| Change Type | Risk | Approach |
|---|---|---|
| Polyfill removal | Low | Remove after verifying browser support |
| Library upgrade (patch/minor) | Low | Update and run tests |
| Library upgrade (major) | Medium | Read changelog, update incrementally |
| Library replacement | Medium-High | Strangler Fig + feature flag |
| Framework migration | High | Branch by Abstraction + long parallel run |
| Architecture change | Very High | Multi-phase plan with Atlas |