Understanding Legacy Application Modernization

What is application modernization?

Application modernization is defined as the process of updating existing business applications (often legacy ones), so they can run on modern platforms, use current architectures, and integrate with today’s digital systems. 

This could mean migrating to the cloud, breaking up monolithic systems into microservices, or refactoring code for performance and security.

Software modernization is a similar, though much broader term. It includes everything from updating operating systems and databases to rethinking infrastructure. However, application modernization focuses on the business applications that drive revenue, operations, and customer experience.

Why is application modernization important?

Numerous enterprises rely on legacy systems. They’ve powered operations for years, sometimes even decades. But as the digital world accelerates, these systems can quickly turn into bottlenecks. They’re costly to maintain, difficult to scale, and risky to integrate with new technologies.

Application modernization is the process of transforming legacy applications into agile, scalable, and secure solutions that align with your current and future business needs. It’s not just about upgrading technology; it’s about unlocking business value, reducing risk, and facilitating innovation.

According to the Red Hat report on application modernization, 53% of respondents undergoing modernization reported seeing scalability benefits; 58% boosted security, while 52% improved reliability.

This highlights the importance of application modernization for three of some of the biggest business goals. Let’s look at some more.

Why modernize applications?

There are some common strategic goals that most organizations aim to achieve when starting their modernization journey. Chief among these are:

Business agility

The ability to pivot quickly in response to market changes is a competitive advantage. Organizations running dated systems can struggle to adapt, necessitating an update to maintain competitiveness.

In fact, 95% of respondents in the Red Hat research believe that application modernization is essential for their organization’s success

Cost efficiency

Modernized applications are cheaper to run and maintain. Experts proficient in maintaining legacy systems become fewer, and as their numbers dwindle, the hourly rate goes way up. Not only that, but the rarer the language, the fewer experts proficient in it, the longer you need to wait for someone to come in and debug whatever’s bugging you. 

Factor in productivity losses to downtime and (expensive) maintenance, which IT departments spend 55% of their budgets on, according to Deloitte – and you see running legacy systems isn’t very cost-effective.

Security and compliance

Legacy systems are often vulnerable and tough to keep compliant. There’s a reason your browser or OS rolls out updates every so often – this is in response to newly developed threats that exploit weaknesses. 

When systems get sunset and security update rollouts stop? You leave your entire business exposed. And there’s nothing malicious actors love more than a vulnerable business system. Legacy system breaches cost upwards of $4.45 million on average.

User experience

Your customers and employees expect seamless, modern digital experiences. However, applications running on legacy systems typically aren’t conducive to providing the sort of UX modern users demand. 

And investing in UX pays. According to a Forrester report, UX investments yielded an astounding 9,900% ROI. That’s not a typo. Good UX removes friction, boosts conversion, keeps MAU figures high, and offers plenty of other benefits, too.

Scalability

Growth shouldn’t be limited by outdated technology. But legacy systems often do not scale.

Researchers at Vrije Universiteit Amsterdam studied the case of a car leasing system written in COBOL. It was found that rewriting to scale would take over 2,800 person months to rewrite the code for the legacy system. 

Attempts at automated modernization also failed, owing to the constraints of the legacy system architecture. This hinders any attempts at scaling the legacy systems noted in the study.

Types of application modernization

Legacy application modernization

Legacy applications may be the backbone of your business. But they weren’t built for the cloud, mobile, or AI-driven world we live in now. Legacy application modernization is about reimagining these systems for today’s needs, making them faster, more secure, easier and cheaper to maintain.

Legacy application modernization services specialize in untangling complex, mission-critical systems and guiding organizations through the transition.

Business application modernization

Business application modernization focuses on aligning your technology with your business strategy. It’s about ensuring your core processes are as flexible and innovative as the market demands.

Enterprise application modernization

For large organizations, enterprise application modernization means scaling these efforts across dozens or hundreds of applications, and often globally. It’s about building a repeatable, strategic approach that delivers value at scale.

Application modernization strategies

There’s no single path to modernization. The right application modernization strategy depends on your goals, technology stack, and risk tolerance. Here’s a look at the most common approaches:

• Rehosting: AKA “lift and shift”. Move applications to a new environment (like the cloud) with minimal changes. Fast, low risk, but limited long-term benefits.
• Replatforming: Make small tweaks to leverage new platform features (e.g., moving from on-premises to managed cloud services).
• Refactoring: Restructure code to improve performance, scalability, or maintainability without changing core functionality.
• Re-architecting: Redesign the application’s core architecture, often moving from monoliths to microservices.
• Rebuilding/reengineering/reworking: Start from scratch using modern frameworks and best practices.
• Replacing: Swap out old applications for new, off-the-shelf solutions.

A robust application modernization framework helps you evaluate these options and choose the best fit for each application. Next, let’s look at two of the most common strategies.

Refactoring vs rebuilding: Choosing the right approach for modernization

When it comes to modernizing legacy applications, two strategies often come up in conversations: refactoring and reworking. While both aim to improve your application’s performance, maintainability, and scalability, they differ in scope, impact, and business value.

What is refactoring?

Refactoring involves restructuring and optimizing the existing codebase without changing the application’s core functionality or external behavior. Think of it as a tune-up: you’re cleaning up technical debt, improving code readability, and making the system easier to maintain and extend. Refactoring is often the go-to choice when:

• Your application’s architecture is fundamentally sound, but the code has become messy or outdated.
• You want to enhance performance, fix bugs, or prepare the system for future enhancements.
• There’s a need to integrate with modern tools or platforms without a full rewrite.

Benefits of refactoring

• Reduced technical debt
• Improved code quality and maintainability
• Lower risk of introducing new bugs
• Faster development cycles for future features

What is rebuilding?

Rebuilding (sometimes called “reengineering” or “reworking”) goes a step further. It involves making significant changes to the application’s architecture, design, or even its core functionality. This could mean breaking a monolith into microservices, migrating to a new platform, or completely rewriting modules to support new business processes.

Rebuilding is the right choice when:

• The current architecture can’t support your business goals or scalability requirements.
• The technology stack is obsolete or unsupported.
• Major new features or integrations are needed that the existing codebase can’t accommodate.
• You’re aiming for a fundamental shift in how the application delivers value.

Benefits of reworking:

• Enables adoption of modern architectures (cloud-native, microservices, etc.)
• Supports new business models and integrations
• Future-proofs your application for long-term growth
• Can deliver dramatic improvements in performance and scalability

Refactoring or rebuilding: How to decide?

The best approach depends on your application’s current state, business objectives, and available resources. Sometimes, a hybrid approach makes sense: start with refactoring to stabilize the system, then rebuild critical components as needed.

Key considerations:

• Business impact: Will refactoring deliver enough value, or is a deeper transformation needed?
• Risk tolerance: Refactoring is less risky, but rebuilding can unlock bigger opportunities.
• Time and budget: Refactoring is usually faster and cheaper, while rebuilding is a longer-term investment.
• Future needs: If you anticipate major changes ahead, rebuilding may be the smarter play.

Building your application modernization roadmap

Success starts with a plan. An effective application modernization roadmap includes:

1. Application modernization assessment

Begin with a thorough application modernization assessment. Audit your legacy applications to understand what’s working, what’s not, and what’s truly business-critical. This step uncovers technical debt, identifies quick wins, and helps prioritize efforts.

2. Prioritization

Not all applications are created equal. Decide which apps to modernize first based on business impact, technical complexity, and risk.

In fact, according to the Red Hat report, 75% of companies have already completed at least small-scale modernization projects.

3. Strategy selection

Choose the right application modernization strategy for each application. Some may be perfect candidates for rehosting, while others may need a complete rebuild, like the COBOL-based car leasing application mentioned above.

4. Execution

Leverage the right application modernization tools and services. This might include automation for code analysis, migration tools, and DevOps platforms for continuous integration and deployment.

5. Optimization

Modernization is an ongoing process. Continuously measure results, gather feedback, and refine your approach.

Navigating application modernization challenges

Application modernization can be complex. Here are some common application modernization challenges and how to tackle them:

• Cost and complexity: Start small, demonstrate value, and scale up. Use automation to reduce manual effort.
• Integration headaches: Use APIs and microservices to connect old and new systems.
• Security risks: Implement security into every stage with DevSecOps practices.
• Change management: Communicate early and often. Bring stakeholders along for the journey.
• Skills gap: Upskill your team or partner with experts who have real-world experience.

Modernization is as much about people and process as it is about technology.

Modernizing development processes

Modernization isn’t just about technology; it’s about processes, too. Adopting Agile and DevOps practices enables faster, higher-quality delivery of modernized applications. Continuous Integration/Continuous Delivery (CI/CD) pipelines and DevSecOps ensure security and compliance are integrated from the start.

Enterprise application modernization

For large organizations, enterprise application modernization is about more than updating a few apps. It’s about building a repeatable, scalable process that delivers value across the business. That means:

• Building cross-functional teams that include IT, business, and security stakeholders.
• Investing in change management to ensure adoption.
• Leverage application modernization solutions that can scale with your business.

Conclusion

Application modernization is a strategic imperative in 2025. It’s about more than technology; it’s about future-proofing your business, delighting your users, and unlocking innovation. With the right application modernization strategy, tools, and partners, you can turn legacy systems into engines of growth.

Ready to take the next step? Contact us and let’s talk about how we can help you modernize your applications and future-proof your business.