Legacy Code Migration Template

This template guides you through safely migrating legacy code to modern architectures, frameworks, or languages while maintaining functionality and minimizing business disruption.

Sample Prompt

Migrate a legacy monolithic application to microservices:
- Analyze existing codebase and identify service boundaries
- Extract user management functionality to independent service
- Implement API gateway for service communication
- Migrate database schema with zero-downtime approach
- Set up monitoring and logging for new architecture
- Plan phased rollout with fallback procedures

What This Template Covers

  • Legacy system analysis and technical debt assessment
  • Migration strategy planning with risk mitigation approaches
  • Code refactoring techniques for modernization without breaking changes
  • Data migration strategies including schema evolution and synchronization
  • Testing approaches for validating migration accuracy and completeness
  • Deployment strategies for minimizing downtime during transitions

Best Practices

  1. Start with comprehensive documentation of existing system behavior
  2. Use the strangler fig pattern for gradual migration approaches
  3. Implement feature flags to control migration rollout
  4. Maintain backward compatibility during transition periods
  5. Test extensively with both automated tests and user acceptance testing
  6. Plan rollback procedures for each migration phase
  7. Monitor system performance before, during, and after migration
  8. Train team members on new technologies and patterns

When to Use This Template

  • Modernizing applications built on outdated technologies or frameworks
  • Breaking down monolithic applications into microservices
  • Migrating from on-premises to cloud infrastructure
  • Updating applications to meet new security or compliance requirements
  • Improving system performance and scalability through architectural changes

The Script

peep legacy-code-migration