What is application modernization?
Application modernization is the process of updating or replacing the architecture, code, and infrastructure of older — or "legacy" — applications. The term most often refers to switching an application's infrastructure from on-premises to cloud-based, and it usually involves moving from a monolithic application architecture to a microservices or serverless architecture. The goal is to make applications more scalable, maintainable, and cost-efficient, while reducing operational overhead.
Like other types of modernization that have taken place in the business world (such as switching from printed memos to emails), application modernization adapts processes to new technologies in pursuit of greater efficiency. Modernizing legacy applications allows the developers of those applications to benefit from cloud computing, which is more scalable and has a more flexible cost structure than older IT models.
Application modernization is often part of a larger cloud migration or digital transformation effort.
How does legacy application modernization work?
Cloud computing takes place on virtual machines. Cloud services are one or more "abstraction layers" removed from the underlying hardware. This differentiates the cloud from on-premises infrastructure, where applications run on specific servers and within clearly defined networks. The cloud vendor manages the hardware and makes services available through network connections. Because the cloud is architected in this way, cloud computing is more flexible, as it is able to scale on demand and eliminates some of the costs associated with on-premises operations.
While on-premises applications tend to be a single monolithic entity, cloud-hosted application architecture is usually divided into smaller parts that are called upon as needed. Application modernization may involve adapting architecture to this format (though this is not the case for all application modernization strategies).
Key concepts for modernized applications include:
- Microservices: Microservices are small, independently deployed components that each perform a specific function within an application. Each runs in its own environment and can be developed and scaled separately.
- Containers: Containers package application code and dependencies so they run consistently across different environments. They are commonly used in microservices architectures, though not exclusively.
- Serverless computing: This type of cloud architecture breaks down an application into discrete, event-driven functions. Serverless functions are individual pieces of code that only run on demand. Note that many cloud-based applications combine serverless, microservices, and containers into a single architecture, connected via API gateway.
- APIs: Application programming interfaces (APIs) act as a connector for the microservices and functions that compose a cloud-based application and that all run separately from each other. APIs allow an application to call on each service as it is needed.
- Orchestration: Orchestration is the automation of tasks associated with managing containers. An application architecture that includes containers will usually also include some kind of orchestration — Kubernetes being a common one.
- Cloud storage: There are several types of cloud-based storage for application data, including object storage, blob storage, and block storage.
- Cloud-native security: Cloud-native security is designed to safeguard cloud-based application infrastructure while supporting data compliance and governance.
- AI integration: Modernized applications integrate more smoothly with generative AI and agentic AI, which are built on models that run remotely in the cloud rather than locally.
What are the main application modernization strategies?
The most common application modernization strategies are all known by names that (in English) start with "R." Consequently these strategies are called by some "the 5 Rs" or "the 7 Rs."
The "5 Rs" (as originally defined by Gartner in 2010):
- Rehost: Also called "lift and shift," this application modernization strategy is often the fastest to carry out. A monolithic, on-premises application is moved to the cloud and hosted through an infrastructure-as-a-service (IaaS) provider instead of self-managed infrastructure. Rehosting is like taking a house and towing it to a lot across the street.
- Refactor: Refactoring is similar to rehosting, but the application is hosted via platform-as-a-service (PaaS) instead of IaaS. This involves even less overhead and more flexibility, but the application may have to be adapted slightly to the cloud provider's platform. Imagine towing a house to a longer but narrower lot than the lot it was on before and adding a second story to the house to make better use of the space.
- Revise: The "revise" strategy involves partially rewriting the application's code base. Imagine deconstructing a house, then rebuilding it according to a more efficient floor plan.
- Rebuild: This application modernization strategy rewrites the application for deployment through a PaaS provider. Imagine taking a wrecking ball to a house and reconstructing it from the ground up.
- Replace: This strategy discards legacy applications and replaces them with modernized or cloud-based applications that offer similar functionality. Imagine buying an entirely new house.
Other application modernization strategies (or "R"s) include:
- Replatform: This strategy involves making some changes to the code so that the application runs well on a cloud platform, but not as many changes as in refactoring.
- Rearchitect: The application backend is redesigned and partially rewritten to function better in the cloud.
- Repurchase: Similar to the "replace" strategy — a replacement application is purchased from a different vendor than one previously used for the application.
Which application modernization strategy should an organization use?
The right strategy — or more accurately, strategies, as most organizations use more than one — depends on an organization’s goals and available budget. A faster migration with minimal effort and cost often means rehosting is the right strategy initially. For long-term scalability or to support modern development practices like continuous integration and continuous deployment (CI/CD), more extensive changes may be needed. In these cases, rearchitecting, refactoring, or rebuilding applications can better prepare organizations for future demands.
Organizations should determine their goals, timeline, and budget for the modernization process before deciding on strategies.
What are the main steps for application modernization?
The specific steps differ depending on the strategy and the organization, but in general the main phases of application modernization efforts are:
- Preparation: This starts with assessing each application that is a candidate for modernization, identifying its components, finding all of its data, and determining the post-modernization goals for the application (e.g., will it be exposed via API? Will it offer the same or expanded functionality?). Organizations must build flexibility into their plans as they may have to be adjusted in response to unexpected conditions during implementation.
- Modernization: In this phase, organizations carry out the plan defined in the preparation stage, transforming application backends and migrating their data as needed.
- Cutover: Old applications are decommissioned and modernized applications take over their functions. This phase ideally takes place either after or during modernization so that business processes are not affected.
- Continued operation: Organizations continue testing, updating, maintaining, securing, and improving their modernized applications, provisioning more cloud resources as needed.
What are the challenges of application modernization?
Application modernization does cost an organization in terms of time, money, and resources. Developer, DevOps, security, and compliance teams need to budget time for moving, architecting, and securing modernized applications. Internal teams may need to redirect network traffic, decommission hardware, and implement new security measures. Ideally, application modernization efforts end up making an organization more efficient in the long run, however.
What are the benefits of application modernization?
Organizations do not modernize their applications simply for the sake of being "modern" or using the cloud — instead they look to benefit from outcomes such as:
- Faster development: Since the cloud abstracts away overhead and infrastructure, organizations can roll out new features much more quickly.
- Making applications available through API: This allows applications to be integrated with other applications for more efficient development and automated processes.
- Scaling for the future: When organizations buy their own infrastructure, they are limited by how much capacity they buy. But the cloud is practically unlimited (although artificial intelligence is testing the capacity of preexisting data centers).
- Improved application performance: A cloud-based application can be reached from a range of locations without slowing network traffic down by running it through a localized data center (a phenomenon known as "tromboning").
- Future-proofing: The flexibility offered by application modernization strategies allows organizations to take advantage of newer technologies and efficiencies as their needs change.
- Reducing technical debt: Outdated languages, clunky implementations, and declining hardware can be replaced during the modernization process.
- Improved security: Moving applications to the cloud removes many of the security challenges associated with on-premises monolithic applications, although the cloud comes with its own security issues.
Cloudflare helps organizations take full advantage of these benefits. Cloudflare's connectivity cloud consolidates network access, security, threat intelligence, and other services provided by multiple vendors into a single platform, and Cloudflare's developer services provide the tools needed for modernizing applications. Learn how Cloudflare boosts application modernization efforts.