Let’s look into the “7 Rs” cloud migration strategy, according to the expanded model introduced by AWS, as well as When to Use the 7Rs Model

7Rs of Cloud

Retire (Stop using)

This strategy is used when terminating or downsizing legacy applications that are no longer supported by the vendor or useful in production and/or the hassle and expense of migrating to the cloud may not be worthwhile at all. In such instances, business-critical workloads that operate on inefficient legacy frameworks are safely retired as the first step towards the adoption of modern, cloud-native deployments.

Retain (Do nothing now and revisit it later)

This strategy is applicable to applications facing challenges in migrating to the cloud due to incompatibility for example, legal or privacy restrictions, prohibitive costs associated with rehosting, replatforming, refactoring, rebuilding, or relocating, latency concerns, and various other reasons. In such cases, these applications may not be suitable for retirement and should persist in their existing framework.

Enterprises typically decide to retain a workload if it relies on another application that needs to be migrated first or when there’s no immediate business value in migrating the application to the cloud. As for vendor-based applications, an enterprise may also choose to retain if the service provider plans to eventually release a Software-as-a-Service (SaaS) model.

Rehost (Lift and Shift)

The rehost migration strategy is often the simplest way to migrate and it involves leveraging cloud Infrastructure-as-a-Service (IaaS) offerings to redeploy workloads on a cloud instance. The strategy allows enterprises to move an on-prem application and all its dependencies as-is to the cloud.

Without changing the core infrastructure, this approach allows organizations to transfer all application data and workflows to cloud services that match the workload’s existing storage, networking, and compute requirements. Since operational and configuration constructs of workloads remain intact, the rehost strategy is also easy to perform and is suitable for enterprises that lack in-house cloud-native expertise.

Relocate (Hypervisor-Level Lift and Shift)

This strategy involves migrating workloads without impacting ongoing operations, rewriting the application source code, or acquiring new hardware. With this strategy, an enterprise can migrate a collection of servers from an on-premises platform, such as Kubernetes or VMware, to a cloud version of the same platform (e.g. managed Kubernetes services like GKE — Google Kubernetes Engine and EKS — Amazon Elastic Kubernetes Service).

Relocating minimizes downtime and disruption since clients remain seamlessly connected during the migration process. As this strategy doesn’t require significant changes in the configuration and architecture of workloads, it’s not necessary to retrain staff or invest in upgraded hardware, thereby reducing operating expenses. It also makes migration costs more predictable by placing clear limits on scalability.

Repurchase (Drop and Shop)

This strategy involves swapping internally administered systems for third-party managed services commercially available from cloud providers, helping teams to retire legacy systems and to move to a consumption-based, Software-as-a-Service (SaaS) subscription model that ties IT costs to generated revenue.

As the services are built and managed by third-party vendors, the repurchase model reduces operational efforts toward managing infrastructure for in-house teams.

The repurchase option also simplifies and expedites migration while reducing downtime and enhancing scalability and efficient regulatory governance. As the migration approach fully leverages cloud-native capabilities, it’s mostly leveraged for workloads that require enhanced application performance and user experience while minimizing operational overheads.

Replatform (Lift, tinker and shift or lift and reshape)

While this migration strategy may entail a significant investment of time and resources, it is frequently justified by the benefits it offers. Notably, this strategy enhances the flexibility, agility, and resilience of workloads, empowering them with cloud-native capabilities. Enterprises can smoothly migrate applications to the cloud, integrating platform optimizations to leverage these capabilities.

This approach affords organizations the flexibility to select components for modernization in line with the latest technological trends, all while preserving the application’s source code and core architecture. This ensures the continued operation of legacy applications, bolstering cloud-based compliance and security measures. Consequently, it elevates application agility and optimizes return on investment (ROI).

Since the application’s architecture and functionality are retained, teams don’t require extensive training to operate the migrating workloads.

Refactor (Re-architect)

Widely acknowledged as the most intricate migration choice, refactoring entails the comprehensive re-architecting of workloads to seamlessly incorporate cloud-native capabilities. Despite demanding a substantial investment in effort and resources, this strategy stands out as the most forward-looking migration approach. By adopting this approach, applications gain the ability to support advanced features, including serverless computing, autoscaling, and distributed load balancing, positioning them to thrive in evolving technological landscapes.

Refactoring helps break down a monolithic application into microservices to achieve high availability and enhanced levels of automation that are often complex to achieve with in-house deployments. While rearchitecting applications for service-oriented architecture may turn out to be costly during the migration phase, a well-planned resulting framework’s operating costs are substantially lower than operating the legacy framework.