Legacy systems are often core to business operations but expensive to maintain and difficult to integrate. Understanding migration complexity is critical for accurate deal modeling.
Defining Legacy
A system is "legacy" when:
- The technology is no longer actively developed or supported
- Finding skilled developers is difficult or expensive
- Integration with modern systems is challenging
- Maintenance costs exceed industry norms
Common Legacy Patterns
- Mainframe systems: COBOL, AS/400, batch processing
- Client-server apps: VB6, PowerBuilder, Delphi
- Early web apps: Classic ASP, early PHP, ColdFusion
- Outdated frameworks: AngularJS, early Rails versions
Migration Assessment Framework
1. Current State Analysis
- Technology stack inventory
- Business logic documentation (or lack thereof)
- Data model complexity
- Integration touchpoints
2. Migration Options
- Rehost: Move to new infrastructure without changes
- Replatform: Minor modifications for cloud compatibility
- Refactor: Significant code changes for modernization
- Rebuild: Complete rewrite with new technology
- Replace: Adopt off-the-shelf solution
3. Risk Factors
- Undocumented business rules
- Data quality and migration complexity
- Integration dependencies
- User training and change management
Key Takeaway: Legacy migration projects typically take 2-3x longer and cost 2-3x more than initially estimated. Build significant contingency into your models.
