Migrating to newer Java versions from 8 to 17 and beyond can boost application performance by nearly 30%, thanks to advancements in GC, concurrency, and JIT optimizations. However, Java Application Modernization is not a one-size-fits-all process. Organizations typically evaluate three core strategies: rehost, refactor, and rebuild. Each approach comes with its own advantages and challenges. In this blog, we break down these strategies to help you determine which modernization path best aligns with your organization’s goals.

Understanding Each Modernization Strategy

Choosing the right approach starts with understanding what each strategy entails and when it makes the most sense.

Rehost 

Rehosting is a straightforward approach where your existing Java application is moved with minimal or no code changes from its current environment to a new one. The new environment is usually a cloud-based infrastructure, for example, virtual machines in AWS, Azure, or GCP. 

Consider rehosting in the following scenarios: 

• You need to migrate to the cloud quickly to reduce the immediate infrastructure costs.
• The application is not a core system that the business heavily relies on or your team wants to minimize disruption.
• Your organization does not require any new features or major changes in the existing architecture.

Pros: 

The benefits of this approach include speed, minimal disruption to operations, lower initial costs, and immediate infrastructure benefits, such as reduced hardware maintenance.

Cons: 

Rehosting does not address the limitations of the existing system architecture. While it may offer some infrastructure flexibility, scaling the application and enhancing agility can remain constrained without further work. That’s why careful planning is essential before beginning the modernization process.

Refactor 

Refactoring involves modifying and optimizing the existing code to use cloud-native features and run on more modern platforms. This involves breaking down monolithic applications into microservices, adopting containers such as Docker and Kubernetes, or utilizing serverless functions. Refactoring improves the internal structure of the application without changing its external behavior.

You can choose refactoring in the following situations:

• You need to improve the performance or resilience of the applications and make them more scalable.
• You want to utilize the cloud-native features to extend the application’s lifespan.
• The application is highly valuable to the business, and although its architecture may have some issues, they are manageable.
• You need to add new features or integrate with other systems more easily.

Pros: 

Refactoring your applications can increase their agility and lead to better performance. It also optimizes the cost over time due to cloud-native efficiencies and extends the application’s useful life.

Cons: 

Refactoring is more complex than rehosting as it requires a higher initial effort and cost. It demands specialized skills and can encounter unforeseen integration or compatibility issues.

Rebuild 

Rebuilding is a radical approach where businesses completely rewrite the applications from scratch. Organizations use entirely new technologies and modern frameworks, such as Spring Boot and Quarkus. They also adopt modern architectural patterns such as a pure microservices architecture or a serverless-first design.

When to choose it:

• Your existing system is in such poor condition that it is no longer feasible to fix or continue using it.
• The core business logic needs to be completely revamped.
• New business requirements cannot be met by the current system, demanding a fresh start.
• You face intense pressure and competition and need to innovate quickly.

Pros: 

This approach enables your team to innovate and completely eliminate technical debt. It helps achieve optimal performance and scalability, build systems that are ready for the future, and design architecture without constraints.

Cons: 

Rebuilding involves the highest cost, the longest time investment, and significant project risk. It requires extensive planning and resources and can lead to disruption in the business during transition.

Factors to Consider When Choosing a Strategy

You need to evaluate several factors before making the right choice:

• Business Goals & Priorities: Your top priority heavily influences your strategy. Is it about reducing the costs immediately or achieving a faster time-to-market for new features or gaining a long-term strategic advantage through innovation? 
• Application Characteristics: It is necessary to conduct a thorough audit of your applications and answer a few questions: How complex are the applications and their architecture? How severe are the technical issues? What are the application’s dependencies, security needs, and performance requirements?
• Budget & Resources: Select the option that suits your budget and the availability of the staff. Decide if you have the internal skills and capacity for the chosen path, or whether you’ll need to bring in external expertise.
• Risk Tolerance: How much disruption can your business operations withstand? What level of risk are you willing to accept for a failure in the project? How complex will the data migration be?
• Timeframe: What is the shortest duration in which you need to achieve the results? What’s the acceptable downtime during the modernization process?
• Vendor Lock-in Concerns: Are you aiming for maximum portability across cloud providers, or are you comfortable leveraging specific, powerful cloud services that might tie you to a particular vendor?

The Decision-Making Framework

To make an informed choice, consider a structured approach:

1. Assessment Phase: Start with a detailed application audit in which the code, architecture, and dependencies are reviewed. Conduct a business value analysis to understand how critical the applications are for your business and the value they contribute. Perform a cost-benefit analysis for each strategy to estimate the potential ROI that can be achieved. Finally, conduct a skills gap analysis to check if your internal team is prepared.
2. Strategy Selection: Use the insights from your assessment to create a scorecard that helps you evaluate the strategy against your goals. Identify whether you need quick wins or a long-term strategic investment. Consider a hybrid approach where you rehost some less critical applications, refactor others for performance gains, and completely rebuild a core, highly strategic system.

3. Phased Implementation: If your organization requires larger or more complex modernizations, it is best to choose a phased approach. Start small, learn from early iterations, and prioritize subsequent steps based on their impact on the business and its feasibility.

Conclusion

The best choice among rehosting, refactoring, and rebuilding your applications depends entirely on your business’s unique context, goals, and resources. Assess your existing workflows and weigh the pros and cons of each strategy against your specific needs. Make an informed decision that future-proofs your applications and drives long-term business success.

Need help with modernizing your Java applications? Contact us for a consultation.