Every application is unique—it has its own technical setup, significance, and lifecycle stage. This means a one-size-fits-all migration approach won’t work. To truly maximize the benefits of cloud adoption, strategies must align with each application’s needs.

The "7 Rs" of cloud migration offer a clear framework for moving applications to the cloud. Each “R”—Rehost, Relocate, Replatform, Refactor, Repurchase, Retain and Retire—represents a distinct strategy, addressing factors like cost, complexity, and business goals.

By choosing the right strategy, organizations can simplify migration, minimize risks, and unlock the full potential of the cloud, ensuring a smooth and effective transition for every application.

Migration Strategies

Having discussed the importance of the "7 Rs" of cloud migration strategies as a whole, let's analyze each of these strategies separately along with their use cases.

As depicted in the diagram above, we can place these 7 strategies into the following groups for the ease of our understanding:

I. Simple & Quicker Migrations
II. Migrations With Minor Changes
III. Migrations Needing Major Changes
IV. Migrations To Cloud Not Needed

I. Simple & Quicker Migrations

1. Rehost : lift and shift

Rehosting, often called "lift and shift", is the simplest and fastest migration strategy for moving to the cloud. In this approach, applications and database servers are migrated as-is to the cloud without altering the code or the underlying infrastructure.

This strategy enables organizations to quickly leverage the cloud's operational simplicity, laying the foundation for future modernization or upgrade initiatives.

Rehosting is the go-to strategy for large-scale migrations where speed is a priority. However, it focuses on rapid transition rather than optimizing costs or unlocking architectural flexibility offered by cloud environments.

To streamline and automate rehosting, AWS offers a suite of powerful tools:

• AWS Migration Hub
• AWS Application Migration Service
• AWS Cloud Migration Factory Solution
• VM Import/Export

During this migration process, your application continues to be live. This minimizes disruption and downtime and the downtime is only limited to your cutover time.

Sample Use Cases:

1. Rehost with Existing Configuration: An organization has virtualized its servers on-premise using VMware and wants to move to cloud without any major changes in it's server configurations.

Using the rehost strategy, the organization can use AWS Application Migration Service to replicate virtual machines to Amazon EC2 instances. The existing VM configurations are rehosted as EC2 instances, allowing seamless migration without major modifications.

2. Rehost Servers at Scale & Modernize Later: We can use AWS Application Migration Service (AWS MGN), a highly automated lift-and-shift (rehost) solution to lift-and-shift a large number of physical, virtual, or cloud servers without compatibility issues, performance disruption, or long cutover windows. This can expediate the process of migration, so that the long term modernization plans can be taken up later as per the organization's budget and schedules.

2. Relocate : hypervisor-level lift and shift

Relocate, also known as "hypervisor-level lift and shift", is very similar to Rehost but focuses on migrating an entire virtualized infrastructure—such as a data center—to the cloud without changing the application setup. It leverages the same virtualization technology in the cloud, making the transition seamless.

• Example: Migrating all virtual machines from a VMware environment in your data center to VMware Cloud on AWS, preserving all configurations.

Relocate can also be used to move resources between different AWS environments:

• Transfer instances or objects to a different VPC, AWS Region, or even a different AWS account.
• Example: Moving an Amazon RDS instance to another VPC or AWS account.

Similar to Rehost, Relocate minimizes disruption and downtime because applications continue serving users during migration. It is the quickest way to move workloads to the cloud, as it doesn’t require changes to your application’s architecture.

II. Migrations With Minor Changes

3. Replatform : lift-tinker and shift

Replatforming involves migrating applications to the cloud with small, strategic modifications to improve efficiency, reduce costs, or take advantage of cloud-native features—without completely re-architecting the application.

Sample Use Cases:

1. E-commerce Application: Move a mid-sized e-commerce application to AWS Elastic Beanstalk to leverage its automatic scaling and management features.
2. Database Migration: Transition a self-managed database to Amazon RDS. By doing so, AWS handles tasks like backups, patching, and scaling, freeing up the team to focus on application development.
3. Serverless Transformation: Move an on-premises application to a serverless architecture (e.g., AWS Lambda) to achieve cost savings and operational simplicity.

Replatforming strikes a balance between speed and optimization, making it ideal for organizations looking to gain immediate cloud benefits with minimal effort.

III. Migrations Needing Major Changes

4. Refactor : Re-Architect for Cloud Optimization

Refactoring focuses on restructuring and modernizing applications to fully optimize them for cloud environments. This often involves leveraging microservices, serverless architectures, or other cloud-native solutions to improve scalability, flexibility, and performance.

Refactoring is ideal for organizations aiming for long-term cloud optimization, enabling modern architectures that deliver greater agility and cost efficiency.

Sample Use Cases:

1. Breaking Monolith into Microservices:
   Decompose a monolithic application into microservices and deploy them using Amazon ECS (Elastic Container Service). This improves scalability, flexibility, and makes development and maintenance more efficient.

2. Modernizing Chatbot Systems:
   An organization migrates and enhances its chatbot system by refactoring its logic into AWS Lambda functions integrated with Amazon Lex (a natural language processing service).

• When a user interacts with the chatbot, Lex triggers the corresponding Lambda function.
• Result: A highly responsive, event-driven chatbot that scales automatically based on demand, ensuring efficient and personalized user interactions.

5. Repurchase : Drop and Shop

Repurchasing involves replacing existing software with cloud-native alternatives to become cloud-ready or accelerate modernization. This strategy often uses Software-as-a-Service (SaaS) solutions to leverage advanced features, reduce maintenance overhead, and improve overall efficiency.

Repurchasing is a straightforward way to adopt modern cloud solutions, enabling organizations to benefit from ready-to-use tools without extensive re-architecture.

Sample Use Cases:

1. CRM Modernization: Replace an on-premises CRM system with a SaaS solution like Salesforce to access advanced CRM capabilities and improved scalability.
2. Financial Software Migration: Move from traditional financial software to AWS QuickBooks, a cloud-based accounting solution, to streamline financial operations and reduce infrastructure management.

IV. Migration to Cloud Not Needed

7. Retain : Keep Applications On-Premise

The Retain strategy involves keeping certain applications on-premise due to regulatory, technical, or compliance constraints.

For organizations seeking the operational simplicity of AWS while retaining applications on-premise, AWS offers tailored solutions like AWS Outposts, AWS ECS Anywhere, and AWS EKS Anywhere. These services enable seamless integration between on-premise infrastructure and AWS cloud environments.

Sample Use Cases:

1. Retain applications handling sensitive customer data on-premise due to legal or regulatory requirements, while migrating non-sensitive workloads to the cloud.
2. Keep a mission-critical legacy application on-premise that cannot be migrated due to compliance constraints or technical limitations.

6. Retire : Eliminate Redundant Applications

The Retire strategy focuses on identifying and removing obsolete or redundant applications to streamline operations and reduce costs.

Sample Use Cases:

1. Phasing out an outdated API endpoint and directing customers to adopt the new, advanced version.
2. Eliminating an obsolete monitoring system and replacing it with a standardized alternative used across other applications.