Why Migration Strategies Matter
Not all workloads can be migrated the same way. Some apps may need only a lift-and-shift, while others must be modernized for scalability and cloud-native benefits. As a Solution Architect, you must map workloads to the correct strategy based on business, technical, and compliance requirements.
The Four “R”s of Migration
1. Rehost (“Lift-and-Shift”)
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Move workloads to Azure with minimal/no changes.
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Fastest and simplest path.
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Tools: Azure Migrate, ASR.
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Example: Moving VMs to Azure as-is.
Pros: Quick, minimal disruption.
Cons: Doesn’t leverage cloud-native features; may cost more long-term.
2. Refactor (“Repackage”)
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Make small changes to use Azure-managed services.
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Example: Move app from VM-based SQL Server → Azure SQL Database.
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Example: Package monolithic app into containers without full redesign.
Pros: Gains some PaaS benefits, reduces ops burden.
Cons: Limited modernization; code changes required.
3. Rearchitect
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Redesign the application to be cloud-optimized.
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Break monolithic app into microservices.
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Use modern architectures (AKS, Functions, Service Bus).
Pros: Scalability, agility, cost efficiency.
Cons: More time and development effort.
4. Rebuild
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Completely rebuild app as cloud-native.
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Use serverless, containers, modern CI/CD pipelines.
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Example: Replace legacy CRM with a new SaaS or custom cloud-native solution.
Pros: Maximum modernization, fully optimized for cloud.
Cons: Most expensive and time-consuming.
How to Choose the Right Strategy
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Business Drivers
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If speed-to-cloud is key → Rehost.
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If reducing ops overhead is critical → Refactor.
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If long-term scalability matters → Rearchitect or Rebuild.
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Application Criticality
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Mission-critical, high-growth apps → Rearchitect/Rebuild.
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Legacy apps nearing retirement → Rehost/Refactor.
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Budget & Timeline
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Limited time/resources → Rehost.
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Investment available for modernization → Rearchitect/Rebuild.
Example Enterprise Scenario
A logistics company needs to migrate:
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Legacy payroll app (end-of-life soon).
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Customer-facing portal needing global scale.
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SQL-based app with high admin overhead.
Correct strategies:
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Payroll app → Rehost (keep as-is until retirement).
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Portal → Rearchitect into microservices on AKS.
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SQL app → Refactor into Azure SQL Database.
Confusion Buster
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Rehost vs Refactor
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Rehost = no code changes.
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Refactor = minor code/config changes.
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Rearchitect vs Rebuild
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Rearchitect = redesign existing app.
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Rebuild = build from scratch.
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Lift-and-Shift vs Modernization
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Lift-and-shift = fast but limited long-term gains.
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Modernization = slower but better ROI.
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Exam Tips
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“Which strategy moves workloads with no code change?” → Rehost.
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“Which strategy uses containers without full redesign?” → Refactor.
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“Which strategy breaks monolithic into microservices?” → Rearchitect.
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“Which strategy builds new app cloud-native?” → Rebuild.
What to Expect in the Exam
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Direct Q: “Which migration strategy is fastest with minimal changes?” → Rehost.
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Scenario Q: “Company wants to reduce SQL admin burden by moving to managed DB.” → Refactor.
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Scenario Q: “Company needs app redesigned for global scale.” → Rearchitect.
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Trick Q: “Rehost and Rebuild require the same effort.” → False.