Legacy app modernization: A comprehensive guide 

Iryna Hnatiuk


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April 22, 2024


modernize legacy applications

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Legacy systems are a headache and, sometimes, a burden for product owners. Outdated apps are usually difficult and expensive to maintain. You need people familiar with old-school technologies to keep them afloat, and you need to invest time and money in making tiny changes or adjustments. What’s the decision? Legacy app modernization.  

From a tech side, the app becomes easy to maintain and update. From a business side, modernization saves money and allows your app to enter new markets sooner. In this analysis, we share the experience of our tech specialists and business analytics. We shed light on steps, strategies, and trends in legacy application modernization. Also, you’ll find out, how to understand that your app requires modernization and what to expect when it’s done. 

What is legacy application modernization? 

First, let’s define the legacy app. That’s a definition of a system, a piece of software, or a whole technology which does not integrate with new technologies and is, therefore, hard to maintain and support. Besides these difficulties, companies can not just abandon these systems. The first reason why is that they might be incredibly complex, and the development of a new similar system might cost a fortune. Also, the systems might be pillars of the business, and the transition to new ones might be risky. The process also requires educating people about new systems and time for polishing all the processes.  

Legacy app modernization is updating the system entirely or partially. The aim is to include modern platform infrastructure, architecture, or features. It results in improved scalability and increased performance and functionality. 

Why and when you should modernize legacy applications? 

Now, let’s talk about markers of an outdated application. They signal you that it’s time to plan modernization.  

First, pay attention to how much money you spend on maintaining your systems. If it becomes costly and the investments seem even higher in the future — that’s a red flag. Another one is that you struggle with integrating new features. This one is hard to ignore because you’ll need to make more and more such integrations in future.  

Problems with security and compliance mean that legacy app modernization is not even an option but a requirement. They question the possibility for you to use the app at all. It leads us to the next red flag — appearing obstacles to your business growth. If your development plan and your systems’ tech abilities don’t match, it’s time for updates. 

You might miss some signals, but your users will also let you know if there are problems. If the user experience becomes insufficient or the app can’t withstand the competition — start thinking about modernization.   

What to expect from legacy application modernization? 

Modernizing the legacy app helps to eliminate risks that arise from using outdated technology. It positively affects all the processes and workspaces. Employees and customers get a better user experience, loyalty grows, and you get more freedom in planning your growth goals. You will only see reductions in spending and maintenance efforts. The list of main outcomes might look the following way: 

  • easier management and maintenance; 
  • reduced costs; 
  • better integration with new systems and features; 
  • access to more scalable SaaS apps; 
  • improved management; 
  • compliance with the latest security requirements; 
  • meeting users’ expectations. 
modernization of legacy applications

The 7 R’s of legacy application modernization process 

Choosing the correct modernization strategy might be tricky. Each one has its place in a modernization initiative, and the choice depends on many factors, including business objectives, budget, time frames, and the current state of the app. Let’s look at 7 R’s of legacy app modernization: 


Often referred to as “lift and shift,” this strategy involves moving an app from its current hardware environment to a new one without making any change to its code. This is typical to migrating to the cloud. It is a quick and cost-effective way to start the modernization process, although it does not improve the app’s architecture, features, or performance. 


This strategy involves restructuring and optimizing the existing code without changing its external behavior. It is more about improving maintainability, scalability, or performance. Refactoring is essential when an app needs to align with new business requirements or technology standards. 


This approach significantly changes the application’s architecture while preserving its purpose and functionality. This might include moving from a monolithic architecture to a microservices architecture. Rearchitecting is necessary when your business wants to take advantage of newer capabilities, like better scalability or resilience. 


This strategy involves completely rewriting or re-coding the app from scratch. Its scope and specifications remain unchanged. This is often chosen when the existing codebase is too outdated or complex and, therefore, can not be effectively refactored or rearchitected. Rebuilding an application allows using modern languages, frameworks, and best practices. 


As the name implies, this involves replacing the old application with a new one. This option is considered when the existing application is no longer viable to maintain or update. It is also an option for when there is a better solution available that meets the business needs. 


In some cases, the best approach is to retire an old application. This is chosen when it no longer provides business value or is redundant due to other modernized apps. It involves a safe decommission of the old application and ensuring that necessary data is migrated to other systems. 


Finally, there might be situations where the best decision is to retain the application as it is. This might an option is it still meets business needs or when modernisation costs outweigh the benefits.  

modernizing legacy applications

Steps for modernization of legacy applications 

App modernization might be time-consuming and complex. The process takes several steps, and each one reaches a different goal and provides a different value. Here is a generalized step-by-step approach to modernization.  

  1. Assessment and planning. Begin by identifying which of your applications can be considered as legacy and require modernization. Understand the business needs and how these apps are aligned with your current and future business goals. 
    Assess the current state of these applications, including their architecture, technology stack, functionality, and performance. Consider any constraints and potential risks involved in the modernization process, including those time and budget related. 
  1. Defining the strategy. Choose the appropriate modernization approach — one of the 7 R’s — for each application based on the assessment. Define clear objectives — what you aim to achieve through modernization. It might be improved performance, scalability, or cost savings. 
    Develop a detailed roadmap and timeline for the process. 
  1. Preparation. Ensure you have the right skills and resources in-house. Provide training for your team, if needed, or hire a modernization partner. 
    Prepare the necessary infrastructure, especially if you are moving to cloud-based solutions. Make sure that the process aligns with relevant compliance standards and incorporates strong security measures. 
  1. Modernization. Enrol the modernization process according to the chosen strategy. Use CI/CD pipelines for efficient and error-free deployment. Rigorously test the apps to ensure they meet quality standards and business requirements. 
    If your strategy involves moving data, plan how this will be done without data loss. Run the data migration, ensuring minimal downtime and impact on business operations. 
  1. Monitoring and optimization. When the app is modernized, continuously monitor its performance. Collect feedback from users and stakeholders to understand the impact of the changes. 
    Keep optimizing your system for better performance, user experience, and cost-effectiveness. 
  1. Documentation and training. Ensure all documentation is updated to reflect every change in the system. Conduct training sessions for your team and users to help them with getting used to the new features. 
  1. Post-modernization review. Evaluate the success of the modernization project against the initial objectives and plan for any further improvements. 

Trends in legacy application modernization  

When kicking off the modernization process and conducting research, pay rigorous attention to the latest technology trends. This way, you make your app compatible with modern apps and make your product one hundred percent up-to-date. Among the trends to pay attention to at the beginning of 2024 are: 

Cloud applications. Sharing data across multiple tools, users, and locations is never as easy as when using a cloud. It also positively impacts scaling and management, allows for agility and improves user experience. Last but not least, making updates takes minimum effort and minimum time. 

Containers. While working in a cloud, use containers to deploy and operate your software. Containers ease management while being moved and distributed between environments. They also make apps more secure, efficient, and accessible. 

Microservices. If the whole app is a tree, then microservices are bunches. They are the parts of one big system that operates for one big goal. However, each of these microservices is tied to deal with specific needs. They are interconnected by APIs and can be combined in different variations. 

Automation. Many processes and actions can be automated to save time and improve productivity. A team can focus on more important tasks that require brainstorming or a creative approach.  

DevOps. It is better for development and operations to work together. It improves overall operational efficiency and helps the business to stay on top. DevOps uses analytics, monitoring, and metrics to make strategic modernization decisions. 

Data warehouses. The amount of data is growing and growing. Data warehouses store it, organize, and protect it. Thanks to these virtual houses, you can be sure that your valuable data will not end up in the wrong hands and will not get lost. 


Legacy app modernization is not just a technological necessity but a strategic movement for businesses that aim to stay competitive. Legacy systems, with their associated complexities and high maintenance costs, can become a significant obstacle to growth and innovation. Modernization unlocks new possibilities, reduces costs, and positions your business for future success. 

Legacy application modernization with Blackthorn Vision  

Blackthorn Vision is your trusted partner in legacy app modernization. We deliver tailored solutions to transform your outdated apps into agile, efficient assets for your business. We follow the latest technology trends and ensure your systems have the most modern features like cloud computing, microservices, and automation.  

We also provide comprehensive support, and our priorities are security, compliance, and maintaining a client-centric approach. Contact us if you are considering modernizing legacy applications to unlock their full potential and come closer to your business objectives. 

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