The Rs of Application Migration & Modernization: 8 Proven Strategies

Explore 8 strategies for app modernization: Rehosting, Refactoring, Rebuilding, Replacing, Replatforming, Relocating, Retiring, and Retaining applications.



When it's time to modernize your business's technology, having a clear plan is essential. Fortunately, there's a well-established framework called "the Rs of application modernization" that simplifies this task. This framework outlines key strategies to evaluate your applications: keeping them unchanged, decommissioning them, migrating them with minimal adjustments, optimizing them for a better cloud fit, or completely redesigning them.

Selecting the right strategy to modernize involves assessing several factors: the current performance of the application, your business objectives, budget constraints, and the desired timeline for the transition.

These strategies aren't all mandatory; think of them as a toolkit from which you can choose the most relevant options for your unique business needs. Each "R" provides a distinct approach to managing your applications, offering the flexibility to tailor the modernization process to your specific requirements.

Let’s dive into each strategy to understand how they can serve your business's modernization efforts. As we explore these strategies for application modernization, it's crucial to have the right expertise and tools at your disposal.

Contact StratusGrid to discover how our AWS Cloud Native Development Services can drive your business forward.

1. Rehost: The Fast Track to Cloud Migration

Rehosting, commonly referred to as "lift and shift," is a strategy for migrating applications to the cloud without altering their underlying architecture or functionality. This approach is characterized by its simplicity and speed, allowing businesses to take advantage of modern cloud infrastructure with minimal changes to their existing applications.

Who It's For

Rehosting is ideal for organizations that:

  • Need to migrate quickly due to data center exit deadlines or cost pressures.
  • Have applications that are well-suited for the cloud without requiring modifications.
  • Prefer a phased approach to cloud migration, starting with rehosting before considering more complex strategies like refactoring or replatforming.

Who It Isn't For

Rehosting may not be suitable for:

  • Organizations looking to fully leverage cloud-native features and optimizations.
  • Applications that require significant scaling, flexibility, or performance enhancements that the cloud can offer through more involved migration strategies.
  • Companies aiming to address and rectify existing technical debt or architectural inefficiencies as part of the migration process.

Read our blog on The Benefits of Cloud Migration –And The Risks of Ignoring It here.

Ideal Applications for Rehosting

Identifying applications that fit this profile can streamline the migration process and ensure a smooth transition. Ideal candidates for rehosting typically include:

  • Stable, mature applications that require little to no active development or updates.
  • Stateless applications that do not store user session information between requests, making them simpler to migrate.
  • Monolithic applications with straightforward architectures, where the entire application operates as a single unit.
  • Applications highly compatible with cloud infrastructure, needing no specific hardware or local dependencies.
  • Non-critical legacy systems that continue to provide value without necessitating immediate modernization.
  • Applications needing immediate scalability to handle varying loads without architectural changes.
  • Software with flexible licensing that does not incur additional costs in a cloud environment.
  • Compliance-driven applications that can maintain regulatory standards post-migration without extensive modifications.

Pros of Rehosting

  • Speed and simplicity: Enables rapid migration to the cloud with minimal disruption to business operations.
  • Cost-effective initial step: Low upfront investment is required compared to more complex migration strategies.
  • Reduced risk: Limits potential errors and issues by maintaining existing application architectures and functionalities.
  • Immediate infrastructure benefits: Provides quick access to the scalability, resilience, and operational efficiencies of cloud environments.

Cons of Rehosting

  • Limited cloud optimization: Does not take full advantage of advanced cloud-native features and capabilities.
  • Potential for increased long-term costs: Without optimization, cloud resource costs can escalate.
  • Unaddressed technical debt: Existing inefficiencies or architectural issues within the application are carried over to the cloud.
  • Scalability and performance constraints: May not adequately address the need for dynamic scaling or performance improvements.

Best Practices for Rehosting

If you’re considering rehosting your applications, consider the following best practices:

  • Before fully committing to the cloud, conduct extensive testing to ensure that applications perform as expected in the new environment.
  • Ensure applications and their dependencies are compatible with the cloud environment to avoid post-migration issues.
  • Consider rehosting as part of a broader cloud migration strategy, where some applications might be rehosted initially, with plans to refactor or rearchitect them in the future for better cloud integration.
  • Leverage migration tools for efficiency and to reduce manual errors.
  • Review and adapt security measures to align with cloud environments, maintaining or enhancing security postures.
  • Continually monitor application performance in the cloud to identify and address any issues, leveraging cloud services for optimization where possible.

Rehosting offers a practical and expedient path to cloud migration for many organizations, particularly those looking to quickly transition with minimal changes. However, it's essential to weigh the approach's benefits against potential limitations and long-term goals. 

For some applications, especially those critical to business operations, exploring other modernization strategies like refactoring or replatforming might yield greater benefits in terms of agility, efficiency, and innovation in the cloud.

Read our blog on 9 AWS Migration Tools You Need for a Successful Cloud Migration here.

2. Refactor or Rearchitect: For Cloud Efficiency and Application Enhancement

Refactoring, often intertwined with the concept of rewriting or rearchitecting applications, is a strategic approach to application modernization that involves making changes to the code or architecture of an application while preserving its original functionality

This strategy leverages modern architectural patterns such as microservices, containers, and serverless computing to enhance scalability, flexibility, and agility. Unlike the simpler "lift and shift" method of rehosting, refactoring requires a deeper engagement with the application's structure, necessitating careful planning, component identification for refactoring, and robust testing and monitoring throughout the process.

Who It's For

Refactoring is particularly beneficial for organizations that:

  • Aim to add features, scale, or improve the performance of their applications beyond the capabilities of their current environment.
  • Have applications with a strong product-market fit, looking to further capitalize on their appeal through enhanced functionality and cloud-native features.
  • Are prepared to invest time and resources into transforming their applications to achieve long-term benefits in cloud efficiency and operational agility.

Who It Isn't For

Refactoring may not be suitable for:

  • Organizations looking for quick, low-effort migration solutions due to tight deadlines or limited budgets.
  • Applications that are due for decommissioning or do not justify the investment in refactoring due to their limited use or strategic value.
  • Teams lacking in cloud-native development skills or the resources to engage in a complex transformation process. If this is your case, contact StratusGrid for a consultation. We’re AWS Cloud Partners and experts in AWS cloud-native development.

Ideal Candidates for Refactoring

Applications best suited for refactoring generally include those that:

  • Applications requiring enhanced scalability and flexibility to manage fluctuating workloads.
  • Monolithic applications that would benefit from a transition to microservices for better maintainability and deployment.
  • Systems with outdated architectures that hinder integration with modern technologies.

Pros of Refactoring

  • Long-term cost savings: By optimizing resource utilization, refactoring can significantly reduce operational costs in the cloud. 
  • Increased agility: Allows for rapid adaptation to changing business requirements through the addition of new features or modification of existing functionalities.
  • Enhanced resilience: Leveraging cloud-managed services can improve the application's overall reliability and availability.
  • Improved operating performance: Refactoring allows for rewriting the underlying code of an application to enhance its performance in the cloud without changing the app's core functionality, making it especially pertinent for software development and DevOps teams. This form of code refactoring can unlock certain cloud platform benefits, such as those offered by AWS, albeit without harnessing the cloud's full range of capabilities.

If you’re a DevOps engineer looking to optimize AWS costs, consider leveraging StratusGrid's cloud cost optimization dashboard to achieve more efficient cloud resource management.

Cons of Refactoring

  • Resource intensity: It demands a substantial investment of time, expertise, and capital.
  • Complexity: Involves deep architectural changes that require thorough testing to prevent regressions in functionality.

Best Practices for Refactoring

  • Approach the process in phases, prioritizing components that will deliver the most significant benefits from cloud optimization.
  • Implement comprehensive testing strategies to ensure that refactored components maintain their functionality and integrate seamlessly with cloud services.
  • Invest in training and development for your team to build expertise in cloud-native development practices and tools.

Refactoring or rearchitecting represents a commitment to reimagining how applications are developed and operated in the cloud, aiming for a profound enhancement of their scalability, flexibility, and performance. 

While it poses considerable challenges in terms of complexity and resource requirements, the long-term benefits of adopting cloud-native capabilities can significantly outweigh these investments, making refactoring a great strategy in the cloud migration journey for suitable applications.

3. Rebuild: To Craft Future-Ready Applications from the Ground Up

Rebuilding involves creating a new version of an application from the ground up, employing modern development frameworks, tools, and methodologies. This approach is chosen to eliminate technical debt, enhance performance, and integrate new functionalities that align with current and future business requirements. 

It's a strategic choice for applications that are severely limited by outdated technologies or architectures and offers an opportunity to fully embrace cloud-native capabilities.

Who It's For

Rebuilding is ideal for organizations that:

  • Have applications that no longer meet business needs or user expectations due to outdated technology or design.
  • Seek to leverage modern development practices, such as microservices and DevOps, to enhance agility and operational efficiency.
  • Are willing to invest in a comprehensive overhaul to ensure their applications are future-proof and fully cloud-native.
  • Aim to incorporate advanced features and functionalities that were not possible with the original application architecture.

Who It Isn't For

Rebuilding may not be suitable for:

  • Organizations looking for quick, cost-effective migration solutions with minimal disruption.
  • Applications that still effectively serve their intended purpose without requiring significant technological or functional enhancements.
  • Teams with limited resources or expertise in modern development frameworks and cloud technologies, unless external support is provided by an application modernization expert.

Ideal Candidates for Rebuilding

  • Legacy systems that significantly hinder business processes and innovation due to their outdated architecture and technologies.
  • Applications requiring a fundamental redesign to meet new business models, compliance standards, or user demands.
  • Projects where the long-term benefits of a cloud-native application justify the initial investment in time and resources.

Cons of Rebuilding

  • Future-proofing: Embracing the latest technologies ensures the application remains relevant and adaptable to future advancements.
  • Elimination of technical debt: Rebuilding allows for discarding outdated code and architectures, leading to enhanced maintainability and performance.
  • Full exploitation of cloud capabilities: Cloud-native applications can leverage the full spectrum of cloud services, optimizing scalability, resilience, and cost-efficiency.
  • Opportunity for radical innovation: The rebuilding process opens up possibilities for integrating cutting-edge features and optimizing user experiences.

Pros of Rebuilding

  • High investment: The most resource-intensive approach, requiring significant time, expertise, and financial commitment.
  • Risk of over-engineering: The scope of the project can expand significantly if not carefully managed, leading to increased complexity and costs.
  • Adaptation and training: Teams may need to learn new technologies and methodologies, potentially slowing down the initial development phases.

Best Practices for Rebuilding

  • Clearly define the vision, objectives, and scope of the rebuilt application to align with business goals.
  • Regularly involve users and business stakeholders in the development process to ensure the rebuilt application meets their needs.
  • Utilize agile development practices to deliver value incrementally and allow for continuous feedback and improvement.
  • Prioritize cloud-native principles and services to maximize the benefits of the cloud environment, enhancing flexibility, scalability, and performance.
  • Equip development teams with training resources to skill-up on cloud native development concepts.

Rebuilding an application presents an opportunity to radically transform its capabilities, performance, and alignment with business strategies. While it demands a significant investment, the long-term advantages of a modern, cloud-native application can provide substantial returns. 

For those embarking on this journey, leveraging the expertise and solutions offered by AWS cloud application modernization service providers like StratusGrid can be invaluable in navigating the complexities of rebuilding for the cloud era.

4. Replace or Repurchase: To Transition to Advanced Alternatives

The "replace" or "repurchase" strategy involves selecting new cloud-based solutions, typically Software-as-a-Service (SaaS) platforms, to substitute existing applications that no longer align with an organization's evolving requirements. This approach is particularly effective when the current application falls short in functionality or when a cloud-based alternative offers a more cost-efficient and feature-rich solution. 

The replacement process needs a comprehensive evaluation of potential alternatives, with a focus on compatibility, scalability, vendor support, and the complexities of data migration.

Who It's For

Replacing is suitable for organizations that:

  • Encounter limitations with their existing applications in meeting modern business demands.
  • Aim to reduce the overhead associated with maintaining and updating legacy systems by leveraging SaaS solutions.
  • Seek to avoid the complexities and resource requirements of overhauling outdated applications.

Who It Isn't For

The replace or purchase strategy might not be ideal for:

  • Businesses with highly customized applications where off-the-shelf solutions cannot provide the required functionality without significant compromises.
  • Organizations that have developed bespoke applications closely tied to their operational processes and business logic.

Ideal Candidates for Replacement or Repurchasing

  • Legacy applications that demand extensive maintenance, where SaaS alternatives offer improved functionalities and cost savings.
  • Outdated systems that lack support or compatibility with modern operating environments and technological standards.

Benefits of Replacement

  • Modern functionalities: Access to the latest features and integrations that SaaS platforms routinely update, ensuring businesses stay ahead with current technologies.
  • Operational cost savings: Shifting from capital expenditures on infrastructure to operational expenditures on subscription-based models can lead to significant financial savings.
  • Reduced maintenance: The responsibility for updates, security, and infrastructure falls to the SaaS provider, freeing organizations to concentrate on core business functions.
  • Improved security standards: SaaS vendors typically adhere to high-security standards, offering a level of protection that might be challenging for individual organizations to achieve independently.

Challenges of Replacement

  • Data migration complexities: Moving data from legacy systems to new applications can be fraught with challenges, including data loss and compatibility issues.
  • Adjustment period: Transitioning to a new system may require training and adjustment time for users, potentially leading to temporary reductions in productivity.

Best Practices for Replacement

  • Conduct a detailed assessment of potential replacements, considering not just the features but also the long-term viability and support from vendors.
  • Before committing to a full replacement, pilot the new solution with a subset of users to identify any potential issues and ensure it meets business needs.
  • Develop a comprehensive data migration plan to ensure a smooth transition, minimizing data loss and downtime.
  • Involve key stakeholders and end-users early in the process to gather input and ensure the new solution aligns with user needs and business objectives.

Opting to replace an outdated or insufficient application with a modern solution can rejuvenate an organization's application portfolio, and drive efficiency, security, and innovation. While the decision to replace should be made after careful consideration of the specific needs and circumstances, for many organizations, this strategy offers a pragmatic path to modernization without the burdens of redevelopment or extensive customization.

5. Replatform: To Unlock Superior Cloud Performance

Replatforming is the middle ground between rehosting and refactoring. It focuses on making essential optimizations to an organization's existing cloud platform to derive benefits without overhauling the core architecture of its applications. For example, you can replatform a Microsoft SQL Server database to Amazon RDS for SQL Server, or move an eCommerce from Microsoft Azure to AWS to save on costs.

This strategy strikes a balance between maintaining the essence of the application and enhancing its performance and cost-effectiveness in the cloud environment. By adopting services like Database-as-a-Service (DBaaS), organizations can streamline operations, reduce licensing costs, and achieve a more efficient cloud presence.

Replatforming vs. Refactoring

Replatforming involves minimal changes to an application's code to adapt it to a new cloud environment without altering its core architecture, aiming for quick cloud benefits like cost reduction and improved scalability. In contrast, refactoring is a more in-depth process that restructures the application's code, and possibly its architecture, to fully leverage cloud-native features, focusing on long-term benefits such as enhanced agility, performance, and scalability. 

While replatforming offers a balance between maintaining existing functionalities and gaining some cloud efficiencies, refactoring demands a greater investment in time and resources to transform the application for optimal cloud utilization.

Replatforming vs. Rehosting

While rehosting is primarily about moving applications to the cloud with no changes, replatforming involves making some optimizations during the migration process to leverage cloud features more effectively, without undertaking a full-scale rearchitecture or rewrite of the application.

Who It's For

Replatforming is most beneficial for organizations that:

  • Wish to enhance their cloud infrastructure with minimal changes to their applications.
  • Are looking to improve performance and reduce costs by leveraging cloud-native features.
  • Seek to maintain the core functionality of their applications while optimizing for cloud efficiency.

Who It Isn't For

This approach might not be suitable for:

  • Businesses requiring significant application changes to meet new business needs or functionalities.
  • Organizations that are not ready to invest in the moderate effort needed for application optimization during the migration process.

Ideal Candidates for Replatforming

  • Applications that can benefit from cloud-native features without extensive redevelopment or re-architecture.
  • Systems where database management poses operational challenges and costs, which can be alleviated by transitioning to DBaaS platforms.
  • Applications that would achieve significant performance improvements through containerization and modern application platforms.

Benefits of Replatforming

  • Operational efficiency: By leveraging managed services, organizations can reduce the time and resources spent on database and infrastructure management.
  • Cost optimization: Transitioning to cloud-native services can result in lower operational costs and reduced licensing fees.
  • Performance enhancement: Optimizing applications for the cloud can improve speed, reliability, and scalability.
  • Incremental improvement: Allows for gradual enhancements, making it possible to progressively realize the benefits of cloud features without extensive disruption.

Challenges of Replatforming

  • Moderate complexity: Requires a careful assessment of which optimizations will yield benefits without introducing significant risks or complexities.
  • Potential dependencies: Some optimizations may introduce dependencies on specific cloud services or platforms, potentially affecting future flexibility.
  • Knowledge and expertise: Successful replatforming often necessitates a good understanding of cloud-native capabilities and the potential impact on the application.

Best Practices for Replatforming

  • Conduct a thorough analysis to identify which aspects of the application will benefit most from cloud optimizations.
  • Explore and integrate cloud-native services that align with the application's requirements and cloud strategy.
  • Implement changes progressively to manage risks and ensure a smooth transition to the optimized platform.
  • Post-migration, continually monitor performance and costs to ensure the replatforming objectives are being met.

Replatforming is a cost-effective solution to improve performance and operational efficiency. By carefully selecting and implementing cloud-native features and services, organizations can achieve a more resilient, scalable, and efficient cloud environment, ensuring their applications remain robust and responsive to evolving business needs.

6. Relocate: To Simplify Cloud Adoption

The relocate strategy on AWS provides a seamless pathway for organizations to transfer their infrastructure, including servers and applications, from on-premises environments to the cloud.

While both rehost and relocate involve moving applications to the cloud with minimal changes, rehost ("lift and shift") is a broader strategy that encompasses transferring applications from an on-premises environment directly to the cloud, often automated and requiring little to no modification of the applications themselves.

In contrast, relocate specifically refers to moving workloads to a cloud environment while retaining the same virtualization platform, such as transitioning from an on-premises VMware setup to VMware Cloud on AWS, allowing organizations to maintain their existing virtualization tools and practices within the cloud.

The relocate approach is particularly beneficial to minimize operational disruptions, as applications continue to serve users throughout the migration process, ensuring continuity and reducing downtime.

Who It's For

The AWS relocate strategy is suited for organizations that:

  • Need to migrate large server volumes or applications to AWS without significant architectural changes.
  • Aim to transition between different AWS environments, such as VPCs, regions, or accounts, with minimal operational impact.
  • Require a rapid migration process that maintains application availability and minimizes user disruption.

Who It Isn't For

This strategy might not be ideal for:

  • Organizations looking to significantly refactor or re-architect applications as part of their cloud migration.
  • Organizations looking to significantly reduce licensing and infrastructure costs by moving to the cloud

Ideal Scenarios for AWS Relocation

  • Bulk server migrations from on-premises environments to the cloud.
  • Transferring AWS resources, like Amazon RDS instances, to optimize for performance, compliance, or cost across different AWS accounts or VPCs.

Benefits of Relocating to AWS

  • Operational continuity: Ensures ongoing service availability, minimizing disruptions and maintaining user experience during migration.
  • Quick migration: Facilitates one of the fastest pathways to AWS, allowing for immediate operation of workloads in the cloud.
  • No new hardware: Eliminates the need for additional hardware investments, reducing upfront costs and complexity.
  • Preserved architecture: Maintains the existing application architecture, ensuring a smooth transition with minimal adaptation required.

Challenges of Relocating to AWS

  • Limited optimization: May not fully exploit AWS's advanced cloud-native features for application-level enhancements.

Best Practices for AWS Relocation

  • Conduct a thorough analysis of your infrastructure and AWS's relocation capabilities to ensure compatibility and plan for a smooth transition.
  • Continuously monitor migrated workloads for performance and cost-effectiveness, utilizing AWS's management tools to optimize resources post-migration.
  • Review detailed migration patterns and strategies provided by AWS to tailor your relocation plan for maximum efficiency and alignment with AWS best practices.

By maintaining the core architecture of applications and minimizing user disruption, businesses can quickly realize the benefits of AWS's scalable, resilient, and cost-effective cloud environment. With careful planning and the use of AWS's comprehensive migration resources, enterprises can navigate their relocation journey smoothly, ensuring operational continuity and leveraging cloud advantages with minimal downtime.

2 Other R’S of Application Modernization – The Non-Migration Options

When trying to find the best approach for application modernization, you can also encounter two additional, critical considerations: Retain and Retire. While not direct paths to migration, these options represent strategic decisions to either keep certain applications as they are or to phase them out entirely.

7. Retire: To Streamline Your IT Portfolio

Retirement focuses on phasing out applications that have become obsolete, redundant, or no longer provide sufficient business value. This process not only reduces the complexity and cost associated with maintaining outdated systems but also redirects resources towards more impactful applications. 

AWS suggests that a significant portion of an enterprise's IT portfolio may be ripe for retirement, offering an opportunity to enhance operational efficiency and security by eliminating the need to maintain and secure these legacy systems.

The decision to retire an application should consider its data, dependencies, and the potential impact on business processes, ensuring that essential components are preserved or suitably replaced.

These are some of the benefits of retiring the right applications:

  • Cost reduction: Eliminating outdated or redundant applications can significantly decrease maintenance and infrastructure costs.
  • Simplified IT landscape: Reducing the number of applications simplifies management, security, and compliance efforts, focusing resources on high-value systems.
  • Enhanced security: Phasing out older applications reduces vulnerabilities associated with outdated software, improving the organization's overall security posture.

On the other hand, retiring your applications may come with the following challenges:

  • Data and dependency risks: Retiring applications requires careful handling of data and understanding dependencies to avoid business disruption.
  • Potential loss of functionality: There's a risk of losing unique functionalities that off-the-shelf solutions might not replicate, potentially impacting business processes.

8. Retain: To Optimize While Preserving

Retention is the strategic choice to maintain an application in its current state when migration or modernization isn't currently viable or necessary. This approach is often adopted for applications that are critical to business operations but require significant refactoring or are bound by compliance and data residency requirements. 

Retention can also be part of a hybrid strategy, where certain applications remain on-premises while others transition to the cloud, allowing organizations to balance innovation with practical constraints.

The pros of retaining your applications are:

  • Business continuity: Retaining critical applications ensures ongoing operations without the risks associated with migration or modernization.
  • Compliance and control: For applications with stringent regulatory requirements or complex customizations, retention offers a way to maintain compliance and control.
  • Flexibility: Retaining applications provides the flexibility to plan for future modernization at a more suitable time, aligning with budgetary and strategic planning cycles.

Some of the cons of not migrating your applications are:

  • Ongoing maintenance costs: Retained applications, especially legacy systems, can incur significant maintenance and operational costs.
  • Missed opportunities for innovation: By retaining applications in their current state, organizations may miss out on the benefits of cloud-native features and modern architectural patterns.
  • Potential for technical debt: Continuing to rely on older technologies can increase technical debt, making future modernization efforts more challenging.

StratusGrid Can Help Through Application Modernization Services

Application modernization can be a complex journey filled with critical decisions and strategic choices. That's where StratusGrid comes in. Our expertise in modernizing applications within the AWS ecosystem, positions us as your ideal partner. 

Whether it's rehosting, replatforming, refactoring, or deciding to retain or retire, our team is here to offer tailored advice and comprehensive support. Don't let the complexities hold you back; reach out to StratusGrid today for a consultation, and let us guide you toward a modernization strategy that aligns seamlessly with your organizational objectives and enhances your technological capabilities.

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