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Legacy application modernization: A comprehensive approach to modernize your business

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In today’s rapidly evolving business landscape, legacy applications often stand as barriers to progress. These existing systems, characterized by outdated technology and architecture can hinder an organization’s ability to keep up with changing business needs and pose significant security and operational risks. Staying competitive is essential in today’s fast-paced business industry—this is where legacy application modernization comes into play.

By Tasmiha Khan

In this comprehensive guide, we will explore the intricacies of software modernization, its profound importance, strategies for successful implementation, potential challenges and the integration of new technologies. 

Understanding legacy applications 

Legacy applications, in the context of information technology, refer to systems that have been in use for an extended period and typically exhibit the following characteristics: 

  • Outdated technology: Legacy applications often rely on outdated technology, which means they were built using older tools and systems. These outdated technologies can make them incompatible with modern standards and best practices. 
  • Inefficient performance: These systems might suffer from inefficiencies and slow response times that hinder productivity. 
  • Security vulnerabilities: Due to outdated security measures and lack of updates, legacy applications are more susceptible to cybersecurity threats. 
  • High maintenance costs: The need for ongoing maintenance and support for legacy applications can result in escalating costs over time. 
  • Limited scalability: Scaling these systems to accommodate growing demands can be challenging and costly. 
  • Poor adaptability: Legacy applications might not easily adapt to changing business requirements, making them ill-suited for modern, dynamic organizations. This is one of the main issues with legacy applications. They are often built on legacy code, which can be poorly written and annotated. This results in knowledge silos, which can be a huge strain on an organization when employees move on. Their successors may find it very hard to understand the code that’s been written, blocking the progress to making changes. 

Approaching legacy system modernization

Legacy system modernization is the process of upgrading or transforming outdated, often monolithic and inefficient legacy systems into more contemporary, efficient and adaptable solutions. Developing a solid app modernization strategy is key to success. This strategy helps guide you through the process of adopting microservices, encapsulating legacy software and introducing modernization solutions. The goal is to create a new system that enhances business processes and improves customer experience.

Microservices are a crucial component of modernizing legacy applications. They involve breaking down large, monolithic applications into smaller, more manageable components or services. The practice of encapsulating or enclosing certain data or components within well-defined boundaries is essential to achieve better maintainability in software systems. 

Legacy application modernization is often approached as part of a broader digital transformation initiative. Digital transformation is the process of using digital technologies to create new business processes and customer experiences (or modify existing ones) to meet changing business and market requirements. It often involves the integration of digital technologies and customer-centric approaches to improve business operations and competitiveness. Improving business value often involves enhancing efficiency, reducing costs, and increasing competitiveness.

Benefits of modernizing legacy systems 

Modernization is not necessarily about replacing these applications entirely, but rather about revitalizing them to meet contemporary needs and standards. Modernizing legacy applications offers a multitude of advantages for organizations seeking to remain competitive and efficient:

  • Improved performance and efficiency: Modernization can significantly enhance the performance and operational efficiency of legacy applications, resulting in quicker response times and improved user experience. 
  • Enhanced security and compliance: Upgrading security measures and ensuring compliance with industry standards are integral components of modernization. Doing so helps reduce the risk of security breaches and avoid costly compliance issues.  
  • Better user interface and experience (UI/UX): Modernization often involves revamping the user interface and user experience, contributing to increased customer and employee satisfaction. 
  • Cost savings: Through modernization, organizations can reduce maintenance costs, optimize hosting and better leverage a global workforce, leading to substantial cost savings in the long run. For example, a retail company that has been using a legacy inventory management system for several years is less cost-efficient. This system is outdated, slow and requires constant maintenance to keep it running smoothly. Modernization would reduce maintenance costs and improve employee productivity by speeding up the process. 

Application modernization strategy: Assessment and planning

The journey to modernization begins with a comprehensive assessment of your organization’s applications and systems. This assessment aims to evaluate the current state, strengths, weaknesses, and potential areas for improvement. After a thorough assessment, the next crucial step is to develop a clear modernization strategy aligned with your business goals and objectives. A well-crafted modernization strategy ensures that the efforts are focused, cost-effective and designed to yield the desired outcomes. 

As part of the assessment and planning phase, consider various modernization approaches. The IBM topic page addressing application modernization highlights the following:

“The most important way to start any application modernization project is with an application assessment. Taking an inventory of what you have is almost always one of the most obvious ways to start a transformation like this. Once you have a list, you can start plotting all of those applications against an x and y axis of ease/difficulty and potential increased value if modernized.” 

Five key modernization strategies 

Modernizing legacy applications can take various forms, depending on the specific needs and circumstances of your organization. The choice of strategy depends on factors like the current state of the application, budget constraints and the desired outcome. Some common strategies include the following: 

  1. Rehosting: Rehosting involves migrating legacy applications to a new environment with minimal changes to the existing code and functionality. It’s a suitable choice when a quick transition is required, but it may not leverage the full potential of modernization. Understanding the code structure is essential in understanding the organization and arrangement of source code in a software application.
  2. Refactoring: Refactoring is the process of restructuring and optimizing existing code to improve its performance and maintainability without altering its core functionality. This strategy can be effective for enhancing an application’s efficiency.
  3. Replatforming: Replatforming entails moving legacy applications to a different platform or infrastructure. This can lead to performance improvements and scalability, but it involves some level of code adaptation.
  4. Re-architecting: Re-architecting involves a comprehensive redesign of the application’s architecture to meet modern standards. It often requires a phased approach, effectively managing the process while addressing architectural issues.
  5. Full replacement: In cases where legacy systems are too outdated, a full replacement may be necessary. While this strategy provides a fresh start, it comes with the challenge of potential disruptions during the transition. 

Potential challenges and solutions

Modernization journeys will vary organization to organization, but there are a few very common aspects that many modernization efforts must address.

Technical debt

Modernizing legacy apps can be a complex undertaking, often hindered by technical debt. Technical debt is a metaphor in software development that refers to the consequences of choosing a quick solution to a problem instead of a more comprehensive and responsible approach. Like financial debt, it represents a trade-off between short-term gains and long-term costs.

Technical debt occurs when software developers or teams make deliberate or unintentional decisions to take shortcuts or compromise code quality in the interest of meeting immediate development goals or deadlines. This is often because it can be time-consuming to effectively update system quality. These shortcuts can result in poor code quality or workarounds that don’t necessarily address the root cause of the issue. 

To address technical debt, you can: 

  • Prioritize reduction: Focus on reducing technical debt within legacy code by restructuring and refactoring to make it more maintainable and adaptable. 
  • Transition to cloud-native systems: Moving toward cloud-native systems can enhance scalability and cost-effectiveness, ensuring that your applications are ready to meet future demands. You might also consider a broader cloud migration strategy (perhaps as part of a digital transformation effort) or a hybrid cloud approach if on-premises solutions are still required. 
  • Embrace a DevOps methodology: DevOps outlines a software development process and an organizational culture shift that speeds the delivery of higher quality software by automating and integrating the efforts of development and IT operations teams. With a DevOps practice, companies can be more agile and more proactive, taking insights into how their software systems are behaving in real-world scenarios into account as they consistently roll out software updates and new features to meet users’ needs.


Security is a core consideration in modernization efforts. Modernization provides an opportunity to reinforce and update security measures. To ensure the security of modernized applications, integrate security early. Incorporate security measures from the beginning of the modernization process, making it a core component of the application’s architecture and design:

  • Conduct a risk assessment: Conduct a comprehensive security risk assessment to identify potential threats that may emerge during modernization.
  • Define requirements and expectations: Clearly define security requirements and expectations for the modernized application. This should cover areas such as data protection, access controls, encryption and regulatory compliance.
  • Ensure compliance: Lastly, ensure that modernized systems comply with relevant regulations and that there is a regular process in place that ensures compliance stays up to date.


The planning aspect really can’t be stressed enough. Create a comprehensive roadmap that outlines how an organization intends to modernize its applications and maintain current moving into the future. It should include goals, methodologies, timelines and resources required for achieving modernization objectives.

To stay competitive and future-proof your modernized applications, consider the following: 

  • Develop APIs: Create application programming interfaces (APIs) to connect modernized systems with existing applications and the broader ecosystem. APIs are crucial for enabling the integration and interaction of various software systems, services, and platforms. 
  • Use frameworks: Frameworks are pre-established sets of libraries, tools and conventions that provide a foundation for developing software applications. They help streamline development by offering ready-made solutions for common tasks.
  • Leverage modern technologies: Incorporate modern technologies like automation, artificial intelligence, cloud computing and other new solutions. This can involve delivering modernized applications with new features and capabilities or even upgrading the entire system infrastructure when necessary.

Overall, it is important to update legacy applications to ensure business growth and to keep pace with the ever-changing business landscape. 

Legacy application modernization and IBM

It’s important to update legacy applications to ensure business growth and to keep pace with the ever-changing business landscape. IBM Instana Observability and IBM Turbonomic can help you get there, with platforms designed to optimize observability, scalability and performance.

IBM Instana’s fully automated real-time observability platform puts performance data in context to deliver rapid identification to help prevent and remediate issues. Instana goes beyond traditional APM solutions by democratizing observability so anyone across DevOps, SRE, platform engineering, ITOps and development can get the data they want with the context they need.

IBM Turbonomic is a performance and cost optimization platform for public, private and hybrid clouds with features that benefit organizations by providing full stack-visualizationintelligent automation and AI-powered insights. Turbonomic allows you to continuously automate critical actions in real-time—without human intervention—that proactively deliver the most efficient use of compute, storage and network resources to your apps at every layer of the stack. As a result, you avoid overprovisioning resources to your cloud environment and only use what you need, resulting in a lower cloud bill and a stronger ROI.

IBM is a leading global hybrid cloud and AI, and business services provider, helping clients in more than 175 countries capitalize on insights from their data, streamline business processes, reduce costs and gain the competitive edge in their industries. Nearly 3,000 government and corporate entities in critical infrastructure areas such as financial services, telecommunications and healthcare rely on IBM's hybrid cloud platform and Red Hat OpenShift to affect their digital transformations quickly, efficiently, and securely. IBM's breakthrough innovations in AI, quantum computing, industry-specific cloud solutions and business services deliver open and flexible options to our clients. All of this is backed by IBM's legendary commitment to trust, transparency, responsibility, inclusivity, and service.

For more information, visit: www.ibm.com.



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