AWS Migration Strategies: The 7Rs Framework Explained

Whether you are moving a handful of applications or orchestrating an enterprise-wide cloud transformation, understanding each of the seven strategies prevents costly missteps and ensures every workload receives the approach it deserves. This guide breaks down each strategy with practical selection criteria, real-world trade-offs, and a decision framework to help you build a migration plan that works.

What Are the 7Rs of Cloud Migration?

The 7Rs are seven distinct approaches to cloud migration that AWS recommends for categorizing and planning application moves. Originally based on Gartner's 5Rs model, AWS expanded the framework to include Relocate and Retain, covering the full spectrum from zero-change moves to complete application retirement.

Each strategy sits along a continuum of effort and cloud optimization. At one end, Rehost transfers workloads with minimal changes. At the other, Refactor rebuilds applications from scratch to exploit cloud-native capabilities. The remaining strategies fill the gap between these extremes, giving migration teams flexibility to match each application to the most appropriate path.

The seven strategies are:

1. Rehost -- Lift and shift without code changes
2. Replatform -- Lift, tinker, and shift with targeted optimizations
3. Refactor -- Re-architect for cloud-native design
4. Repurchase -- Replace with a SaaS or commercial equivalent
5. Relocate -- Hypervisor-level migration for VMware workloads
6. Retain -- Keep on-premises and revisit later
7. Retire -- Decommission applications no longer needed

Rehost: The Lift-and-Shift Approach

Rehosting moves applications to AWS without modifying code, making it the fastest way to exit an on-premises data center. Using tools like AWS Application Migration Service (MGN), teams replicate servers, databases, and configurations directly onto EC2 instances with minimal disruption.

Organizations typically choose this strategy when facing data center lease expirations, compliance deadlines, or when they need to demonstrate early cloud wins to leadership. The trade-off is clear: speed comes at the expense of cloud optimization. Oversized instances, legacy configurations, and technical debt all transfer unchanged.

When Rehost Works Best

• The application is stable with a standardized architecture (web servers, relational databases, batch systems)
• Time-to-migration matters more than immediate cost savings
• The team plans to optimize workloads after the initial move (a common two-phase approach)
• Deep cloud-native expertise is not yet available in-house

Rehost Limitations to Plan For

Because rehosting mirrors on-premises configurations, it does not take advantage of auto-scaling, serverless computing, or managed database services. Cloud spend may initially be higher than expected if instances are not right-sized. Plan a post-migration optimization phase within 60 to 90 days to review resource utilization and adopt AWS-native capabilities where they reduce cost or improve reliability.

Replatform: Targeted Optimizations During Migration

Replatforming applies selective improvements during the migration without requiring a full architectural redesign. Think of it as lifting your application but swapping specific infrastructure components for AWS-managed equivalents. For example, migrating a self-managed MySQL database to Amazon RDS, or replacing a custom caching layer with Amazon ElastiCache.

This strategy strikes a balance between migration speed and meaningful cloud benefits. You avoid the cost and complexity of a complete refactor while gaining improved reliability, reduced maintenance burden, and access to managed service features like automated backups, patching, and scaling.

Common Replatforming Scenarios

• Database migration: Moving to Amazon RDS, Aurora, or DynamoDB for automated backups and failover
• Message queues: Replacing self-managed RabbitMQ or ActiveMQ with Amazon SQS or Amazon MQ
• Container workloads: Shifting to Amazon ECS or EKS for orchestration without rewriting application logic
• File storage: Replacing local or NAS storage with Amazon S3 for durability and scalability
• Runtime upgrades: Updating operating systems or language runtimes as part of the migration

Replatforming Trade-Offs

Each component swap introduces integration testing requirements that rehosting avoids. Tightly coupled legacy applications may not tolerate partial changes without broader adjustments. Budget additional time for compatibility testing and maintain a rollback plan for each component swap. Despite these considerations, replatforming often delivers the best return on effort for applications that do not justify a full refactor.

Refactor: Re-Architect for Cloud-Native Performance

Refactoring rebuilds applications from the ground up to fully exploit AWS cloud-native services, delivering the highest long-term returns in scalability and cost efficiency. This typically involves decomposing monolithic architectures into microservices, adopting serverless functions with AWS Lambda, implementing event-driven patterns, or shifting to containerized deployments on Amazon EKS.

While refactoring demands the largest investment in time and engineering resources, it unlocks capabilities that are impossible in legacy architectures. Organizations pursuing digital transformation often refactor their highest-value applications first, then cascade the patterns and learnings to the rest of the portfolio.

Key Benefits of Refactoring

• Horizontal scalability: Cloud-native architectures handle traffic spikes without over-provisioning, scaling down when demand drops
• Cost efficiency: Serverless and containerized workloads eliminate idle compute costs, with pay-per-use pricing on Lambda reducing baseline spend
• Fault isolation: Microservices contain failures to individual components, preventing cascading outages across the application
• Faster release cycles: Independent services let teams deploy features with lower risk and shorter feedback loops

When Refactoring Is Worth the Investment

Refactoring is most justified when the application is a core revenue driver, when current architecture prevents scaling to meet demand, or when accumulated technical debt makes maintenance unsustainably expensive. It is not the right choice for applications nearing end-of-life or those with low business impact -- in those cases, simpler strategies like rehost or retire deliver better ROI.

Repurchase: Replacing Legacy with SaaS

Repurchasing swaps an existing application for a cloud-native SaaS or commercial product, migrating the business function rather than the technology. Common examples include moving from on-premises CRM to Salesforce, switching self-hosted email to Microsoft 365, or replacing a legacy HR system with Workday or BambooHR.

This strategy eliminates ongoing infrastructure management and places your team on a vendor-supported upgrade path. However, repurchasing requires careful evaluation across several dimensions before committing.

Repurchase Evaluation Checklist

• Total cost of ownership: SaaS subscription fees may exceed self-hosted costs for large user bases over a multi-year period
• Data migration complexity: Exporting data from legacy formats into the new platform can require custom ETL development
• Feature coverage: Off-the-shelf products rarely replicate every custom workflow -- document gaps before committing
• Integration requirements: Evaluate API availability and whether existing integrations can connect to the replacement
• Change management: End users need training and transition support; underestimating this is a common source of failed SaaS adoptions

Relocate: Hypervisor-Level VMware Migration

Relocating moves VMware-based workloads to AWS at the hypervisor level, preserving the application, operating system, and network configuration unchanged. This strategy uses VMware Cloud on AWS to provide a consistent hybrid cloud experience, letting organizations shift virtual machines with minimal disruption.

Relocate is particularly valuable for organizations with heavy VMware investments that need to vacate data centers quickly. It preserves existing operational processes, tooling, and team skills while providing adjacency to the full suite of AWS services.

When Relocate Makes Sense

• Your environment runs on VMware vSphere and application-level changes are not feasible in the current timeline
• A data center lease is expiring and migration speed is the top priority
• You need a hybrid operating model with consistent management across on-premises and cloud environments
• The long-term plan includes eventual modernization, but the immediate goal is infrastructure consolidation

Retain: Deliberately Postpone Migration

Retaining is an intentional, data-backed decision to keep specific applications on-premises when migration is impractical or unjustified in the current phase. This is not the same as ignoring migration. It means the application was assessed, and concrete reasons exist for postponement.

Organizations should document the retention rationale for each application and set a reassessment date -- typically 6 to 12 months later -- to evaluate whether conditions have changed enough to warrant migration.

Common Reasons to Retain

• Latency-sensitive dependencies on on-premises hardware or specialized equipment
• Regulatory or compliance requirements that restrict data location or processing environment
• Recently purchased hardware or software licenses with remaining contractual value
• Applications under active development where migration would disrupt delivery timelines
• Workloads that require specific on-premises integrations not yet available in AWS

Retire: Decommission What You No Longer Need

Retiring identifies and decommissions applications that no longer serve a business purpose, reducing migration scope and cutting ongoing costs. Portfolio discovery during migration planning frequently reveals that 10 to 20 percent of an enterprise application portfolio is redundant, unused, or functionally duplicated by other systems.

The retirement process requires validation. Confirm with stakeholders and usage data that no active users or downstream systems depend on the application. Archive data according to retention policies, update internal documentation, and redirect users to replacement systems before decommissioning.

Benefits of Application Retirement

• Reduces overall migration project scope and associated costs
• Eliminates licensing, maintenance, and hosting fees for unused systems
• Simplifies the application portfolio and reduces operational risk surface
• Frees engineering capacity to focus on higher-priority migration workloads

How to Choose the Right Strategy for Each Workload

The right migration strategy depends on the intersection of each application's business value, technical complexity, and your organization's cloud maturity. AWS recommends beginning with a portfolio assessment using AWS Migration Hub and AWS Application Discovery Service to inventory workloads, map dependencies, and establish a baseline for decision-making.

A practical approach is to score each application on two axes: business criticality and migration difficulty. This creates four quadrants that map naturally to the 7Rs framework:

• Low criticality + Easy to move: Rehost or Retire candidates
• Low criticality + Hard to move: Retain or Retire candidates
• High criticality + Easy to move: Replatform candidates
• High criticality + Hard to move: Refactor or Repurchase candidates

Building a Phased Migration Plan

1. Discover: Inventory all applications and their dependencies using AWS Application Discovery Service or partner tools
2. Assess: Evaluate each application against the 7Rs criteria -- business value, technical debt, compliance requirements, and team readiness
3. Prioritize: Group applications into migration waves, starting with lower-risk workloads to build team confidence and establish repeatable processes
4. Execute: Apply the selected strategy per workload, using AWS migration tools such as MGN for rehosting, DMS for database moves, and CloudEndure for continuous replication
5. Optimize: After migration, right-size instances, adopt Reserved Instances or Savings Plans, enable auto-scaling, and evaluate whether rehosted workloads should be replatformed or refactored in a subsequent phase

AWS Migration Tools That Support Each Strategy

AWS provides a suite of migration tools designed to support each phase of the migration lifecycle, from discovery through post-migration optimization. Selecting the right tool depends on your chosen strategy and the type of workload being moved.

Common Migration Mistakes to Avoid

Migration failures most often result from inadequate planning rather than technical limitations. These are the pitfalls that derail projects across organizations of every size:

• Skipping portfolio discovery: Migrating without a complete inventory leads to missed dependencies and unexpected outages during cutover
• Applying one strategy to everything: Rehosting the entire portfolio avoids complexity up front but creates optimization debt that accumulates quickly
• Underestimating data transfer time: Large datasets moving over network connections can take days or weeks -- factor in AWS Snow Family devices for multi-terabyte transfers
• Ignoring security and compliance: Migration is not the time to defer security. Map compliance requirements to AWS controls before the move, not after
• Neglecting team readiness: Cloud migration requires different operational skills. Invest in training before expecting teams to manage cloud-native infrastructure effectively

How Opsio Supports AWS Migration Projects

As an AWS migration partner, Opsio combines portfolio assessment with hands-on migration execution to ensure each workload lands on the right strategy. Our teams work across DevOps, infrastructure, and security to deliver migrations that are planned methodically and executed with minimal business disruption.

Whether your immediate need is a straightforward lift-and-shift for legacy systems approaching end-of-support, or a phased refactoring program for business-critical applications, Opsio provides the technical depth and migration experience to accelerate your timeline while managing risk. Get in touch to discuss your migration roadmap and receive a workload assessment tailored to your portfolio.

Frequently Asked Questions

What are the 7Rs of AWS migration?

The 7Rs are Rehost, Replatform, Refactor, Repurchase, Relocate, Retain, and Retire. Each represents a different approach to moving applications to the cloud, ranging from simple lift-and-shift (Rehost) to complete re-architecture (Refactor). AWS recommends assessing every application against all seven strategies during the planning phase to select the best fit based on business value and technical complexity.

Which AWS migration strategy is the fastest?

Rehosting (lift and shift) is typically the fastest strategy because it moves applications to AWS with no code changes. Using AWS Application Migration Service (MGN), organizations can replicate servers to AWS and perform cutover with minimal downtime, often completing individual workload migrations in days. Relocate offers similar speed for VMware-based environments.

When should I refactor instead of rehost an application?

Choose refactoring when the application is a core revenue driver that needs better scalability, when accumulated technical debt makes maintenance unsustainably costly, or when you want to adopt cloud-native services like Lambda or containers. If speed is the immediate priority, rehost first and plan to refactor high-value workloads in a later optimization phase.

How do I decide which migration strategy to use for each workload?

Start with a portfolio assessment using AWS Migration Hub to inventory workloads and map dependencies. Then evaluate each application on business criticality, technical complexity, compliance requirements, and team readiness. Plot workloads on a criticality-versus-difficulty matrix and align each quadrant with the most appropriate strategy from the 7Rs framework.

What tools does AWS provide to support migration?

AWS offers Application Migration Service (MGN) for server rehosting, Database Migration Service (DMS) for database moves, Migration Hub for centralized tracking, Application Discovery Service for portfolio assessment, and Schema Conversion Tool for database schema transformation. VMware Cloud on AWS supports the Relocate strategy for hypervisor-level migrations.