Systems Analyst: How do you plan legacy system modernization?

Legacy modernization — evolving old systems to modern architectures.

Assessment:

• Business value: Revenue, users, criticality.
• Technical debt: Code quality, dependencies, test coverage.
• Risk: Security vulnerabilities, compliance gaps.

Strategies:

• Strangler Fig: Gradually replace with new services.

  • Route traffic to new system incrementally.
  • Remove old code after migration.

• Re-platform: Move to new infrastructure (lift-and-shift).

  • Containerize, move to cloud.

• Re-architect: Rewrite with modern patterns.

  • Microservices, event-driven.

• Replace: Buy SaaS solution.

  • If domain is not core competency.

• Retain: Keep as-is if low value, low risk.

Steps:

1. Inventory existing systems.
2. Assess business alignment and technical health.
3. Prioritize by value and risk.
4. Choose strategy per system.
5. Create migration roadmap with milestones.
6. Implement with parallel running.

Challenges:

• Data migration and consistency.
• Training and change management.
• Running old and new in parallel.