🧭 Strategy Selection Guide

Making the right choice between Rehost and Refactor strategies

🎯 Decision Framework

Choosing the right migration strategy is crucial for success. This guide provides a systematic approach to help you make informed decisions.

🔍 Assessment Questionnaire

📊 Workload Assessment

Answer these questions for each application you’re planning to migrate:

🏗️ Technical Characteristics

Question Rehost Score Refactor Score
Application Age    
Legacy (10+ years) +3 0
Mature (5-10 years) +2 +1
Modern (0-5 years) +1 +3
Code Maintainability    
Poor documentation, hard to modify +3 0
Some documentation, moderate changes possible +2 +2
Well-documented, easy to modify +1 +3
Current Performance    
Acceptable, no issues +3 +1
Some bottlenecks +1 +3
Major performance issues 0 +3

⏰ Business Requirements

Question Rehost Score Refactor Score
Migration Timeline    
Urgent (< 3 months) +3 0
Moderate (3-6 months) +2 +2
Flexible (6+ months) +1 +3
Budget Constraints    
Limited budget +3 0
Moderate budget +2 +2
Flexible budget +1 +3
Risk Tolerance    
Low risk tolerance +3 +1
Moderate risk tolerance +2 +2
High risk tolerance +1 +3

👥 Team & Skills

Question Rehost Score Refactor Score
Cloud Expertise    
Limited cloud experience +3 0
Some cloud experience +2 +2
Strong cloud expertise +1 +3
Development Resources    
Limited development capacity +3 0
Some development capacity +2 +2
Strong development team +1 +3

📊 Scoring Your Assessment 

---
title: Strategy Selection Decision Tree
---
flowchart TD
    A[📝 Complete Assessment] --> B{📊 Calculate Total Scores}
    
    B --> C{Rehost Score vs Refactor Score}
    
    C -->|Rehost > Refactor + 5| D[📦 Choose REHOST]
    C -->|Refactor > Rehost + 5| E[🔄 Choose REFACTOR]
    C -->|Scores within 5 points| F[🤔 Hybrid Approach]
    
    D --> G[✅ Fast Migration Path]
    E --> H[⚡ Optimized Cloud Path]
    F --> I[🎯 Phased Migration]
    
    G --> J[📋 Proceed to Rehost Guide]
    H --> K[📋 Proceed to Refactor Guide]
    I --> L[📋 Consider Both Strategies]
    
    style D fill:#f3e5f5,stroke:#4a148c,stroke-width:2px
    style E fill:#e8f5e8,stroke:#1b5e20,stroke-width:2px
    style F fill:#fff3e0,stroke:#f57c00,stroke-width:2px

🎯 Common Decision Scenarios

📦 Strong Rehost Candidates

🏢 Scenario: Legacy ERP System

  • ✅ 10-year-old SAP system with customizations
  • ✅ Critical business operations depend on it
  • ✅ Limited development team familiar with system
  • ✅ Tight migration deadline due to data center closure
  • ✅ Regulatory requirements for infrastructure control

💡 Why Rehost?

  • Minimal disruption to business operations
  • Leverages existing team knowledge
  • Meets urgent timeline requirements
  • Maintains regulatory compliance

🔄 Strong Refactor Candidates

💻 Scenario: Customer Web Portal

  • ✅ 3-year-old .NET application with good documentation
  • ✅ Performance issues during peak traffic
  • ✅ Development team available for enhancements
  • ✅ Cost optimization is a priority
  • ✅ Scalability requirements are growing

💡 Why Refactor?

  • Leverage Azure App Service for better performance
  • Implement auto-scaling for peak traffic
  • Reduce long-term operational costs
  • Improve development and deployment processes

🎯 Hybrid Approach Scenarios

🏗️ Scenario: Multi-Tier Application

  • Database tier: Rehost to Azure SQL VM (complex stored procedures)
  • Application tier: Refactor to Azure App Service (well-architected code)
  • Web tier: Refactor to Azure Front Door + CDN (static content)

🔍 Detailed Decision Criteria

📦 When to Choose Rehost

✅ Technical Indicators

  • Complex dependencies that are hard to untangle
  • Legacy frameworks not supported in PaaS
  • Custom kernel modules or specific OS requirements
  • Third-party software with licensing restrictions
  • Compliance requirements for infrastructure control

✅ Business Indicators

  • Time-critical migrations (data center closure, contract expiration)
  • Limited budget for application changes
  • Risk-averse organization preferring minimal changes
  • Proof of concept for cloud adoption

📊 Example Cost Analysis 

Rehost Costs:
├── 🚀 Migration: $10,000 (low complexity)
├── 💰 Monthly Operations: $5,000 (VM costs)
└── 🛠️ Ongoing Maintenance: High (OS patches, updates)

Total Year 1: $70,000

🔄 When to Choose Refactor

✅ Technical Indicators

  • Well-architected applications with clear separation of concerns
  • Standard frameworks (.NET, Java, Node.js) supported by PaaS
  • Performance bottlenecks that cloud services can address
  • Scalability requirements that benefit from cloud elasticity
  • Integration needs with other cloud services

✅ Business Indicators

  • Long-term cloud strategy with optimization goals
  • Development resources available for modernization
  • Cost optimization is a priority
  • Performance improvement requirements

📊 Example Cost Analysis 

Refactor Costs:
├── 🚀 Migration: $50,000 (development effort)
├── 💰 Monthly Operations: $2,000 (PaaS services)
└── 🛠️ Ongoing Maintenance: Low (managed services)

Total Year 1: $74,000
Year 2+: $24,000/year (significant savings)

🛠️ Assessment Tools

📊 Azure Migrate Hub

  • Automated discovery of on-premises workloads
  • Dependency mapping for application relationships
  • Performance assessment and right-sizing recommendations
  • Cost estimates for different migration strategies

🔍 Application Assessment Tools

  • Azure App Service Migration Assistant for web applications
  • Data Migration Assistant for SQL Server databases
  • Server Assessment Tool for infrastructure evaluation

📋 Decision Matrix Template 

---
title: Assessment Framework Summary
---
flowchart LR
    subgraph Input [📥 Inputs]
        A[🏗️ Technical Assessment]
        B[⏰ Business Requirements]
        C[👥 Team Capabilities]
        D[💰 Cost Analysis]
    end
    
    subgraph Process [⚙️ Decision Process]
        E[📊 Scoring Matrix]
        F[🔍 Risk Assessment]
        G[📈 ROI Analysis]
    end
    
    subgraph Output [📤 Strategy Selection]
        H[📦 Rehost Strategy]
        I[🔄 Refactor Strategy]
        J[🎯 Hybrid Approach]
    end
    
    Input --> Process --> Output
    
    style Input fill:#e3f2fd,stroke:#1976d2
    style Process fill:#f3e5f5,stroke:#7b1fa2
    style Output fill:#e8f5e8,stroke:#388e3c

🎯 Decision Validation

✅ Validation Checklist

Before finalizing your strategy choice:

  • 📊 Assessment scores clearly favor one approach
  • 👥 Stakeholder alignment on chosen strategy
  • 💰 Budget approval for estimated costs
  • ⏰ Timeline feasibility confirmed
  • 🛡️ Risk mitigation plans in place
  • 📋 Success criteria defined and measurable

🔄 Strategy Review Points

Plan to review your strategy at these milestones:

  • 📋 After pilot migration (first application)
  • 📊 Every 10 applications migrated
  • 🎯 At major project phases (quarterly reviews)
  • ⚠️ When issues arise that challenge assumptions

🎯 Key Takeaways

  • 📊 Use the scoring matrix to objectively assess each workload
  • 🎯 Consider hybrid approaches when scores are close
  • 💰 Factor in total cost of ownership, not just migration costs
  • ⏰ Balance speed vs. optimization based on business priorities
  • 🔄 Strategy can vary by application - one size doesn’t fit all
  • 📋 Document decisions and rationale for future reference

📖 Next Steps: