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Guide to legacy systems modernization

Do you rely on an old system that's becoming increasingly expensive and difficult to maintain? Have you built a system and left it untouched, without development, for a long time? Or perhaps you haven't used the software for years, yet it holds the potential to be adapted and restarted? If you find yourself nodding to any of these situations, it's clear that modernizing legacy applications is a pressing matter for you. Stay with us to learn everything you need to know to keep your system updated.



What is a Legacy System?

When developing a system over the years, many companies focus mainly on creating new features. All updates and optimization, which are, after all, essential, are forgotten. As a result, you end up with a technological debt which makes your system no longer efficient, but legacy.

A legacy system refers to older software that has been in use for an extended period, but may no longer effectively support the evolving business needs and new technologies. They often have outdated code structures and limited compatibility. Despite their age, they often support critical functions.

What is Legacy System Modernization?

Legacy system modernization is the practice of updating and optimizing legacy software to enhance its functionality and align it with contemporary business requirements and technologies. This modernization process can involve a variety of approaches and is a challenging but necessary task in updating your system.

Challenges and Threats of Legacy Systems

As you can guess, using legacy systems often is associated with a lot of risk that leads to a lot of trouble.

Which challenges are we facing?


Technical debt

Over time, older software accumulates technical debt. They have legacy code that hinders effective system operation, implementation, and unambiguous estimation and can increase the risk of system failure.

Changed architecture

Legacy application architecture is also not compatible with actual trends and technologies. It makes it difficult to integrate with new solutions and adopt more efficient and scalable technologies.

Security demands

Such software systems also struggle to meet nowadays security standards. This leaves them vulnerable to breaches and data compromises. They demand regular security patches to protect against new threats.

Expensive maintenance

What’s more, maintaining legacy technology becomes increasingly costly. Rising maintenance expenses strain budgets and divert resources from more strategic initiatives.

Reasons to Modernize Legacy System

Effective legacy application modernization offers numerous benefits. We named a few so you know why you need to bet on the legacy transformation.


Reason 1: To better perform

It’s no secret that old applications lack speed and efficiency. However, by embracing modernization services, you can optimize the code structure and functionality and be certain it operates at its full potential.

Reason 2: To remain competitive

If you want to remain competitive, you need to adapt quickly. But with legacy systems, you will lag behind. Bet on a legacy modernization approach, and you will keep pace with competitors, seize new opportunities, and offer customers enhanced services.

Reason 3: To keep your data safe

Legacy app modernization is essential to safeguard data and protect against evolving cyber threats. If you decide upgrading legacy systems, you will have greater control over sensitive information and maintain the trust of customers.

Reason 4: To reduce costs

Old systems can be costly, especially when specialized resources are required to work on outdated technologies. However, legacy modernization is the process that saves money and creates long-term savings.

Legacy System Modernization Approaches

Now you know that transforming legacy systems is a critical stage in the modernization journey. This stage doesn’t always look the same, as there are available different legacy modernization techniques – each with its own pros and cons.



Encapsulation involves isolating legacy code within a new layer to protect it while building new functionalities around it. This approach essentially creates a “wrapper” for the legacy system and shields it from the complexities of modernization.

Pros: Encapsulation allows for the preservation of legacy code and data and reduces risks.

Cons: It may not address underlying structural issues in the legacy system.

Evaluation: This approach is suitable when minimal changes are required. It’s particularly valuable when the legacy system’s core logic remains valuable, and surrounding it with modern components is the most efficient path.


This type of modernization of legacy systems moves old apps to new hardware, cloud, or environment, often without making significant code changes. Due to this, the system operates the same way as before.

Pros: Rehosting minimizes the need for code modifications and reduces project complexity.

Cons: It may not fully connect the system with modern technologies and limit the system’s capabilities.

Evaluation: Rehosting is a pragmatic choice when the goal is to quickly update the infrastructure. This approach is especially effective when the existing legacy application functions well and requires minimal enhancement.


Replatforming involves making minor adjustments to the application to adjust it to the new platform. It supports legacy systems by offering a better performance on new platforms.

Pros: It offers a balance between modernization and preserving older legacy code.

Cons: It won’t leverage the maximum capabilities of new platforms and restricts the potential for innovation or even scalability.

Evaluation: Replatforming is an effective strategy when the primary objective is to improve compatibility and performance without extensive changes in the whole system.


Refactoring entails making strategic changes to the code. It improves its structure, maintainability, and performance. It entails making small and consistent adjustments, analyzing and altering the existing code. The method is safe and effective and supports continuous improvement.

Pros: Refactoring enhances the codebase and aligns it with actual software development practices.

Cons: It can be time-consuming and may require extensive testing.

Evaluation: This approach is beneficial when you need to address code issues and maintain core functionalities.


Rearchitecting involves restructuring the application’s architecture to align it with contemporary standards. It focuses on making fundamental changes to the system’s structure and design.

Pros: The modernization efforts fully exploit the capabilities of modern technologies.

Cons: It can be a complex and resource-intensive process.

Evaluation: Rearchitecting is a good option if you need a comprehensive review of the system architecture. It is suitable for outdated legacy applications that require serious transformation.


Rebuilding implies developing a new app from scratch with modern tools and practices. It is a ground-up creation of a new system to replace the old one as you already know that it will fail in the near future. Take advantage of this approach when patching existing systems takes too long or when the language used to describe them is outdated.

Pros: It offers the opportunity to create a highly efficient, state-of-the-art app.

Cons: It is an expensive approach and may result in a longer modernization timeline.

Evaluation: Rebuilding is best if your legacy systems no longer meet the organization’s needs and you require a fresh start with the latest technologies.

What Steps You Need to Take to Modernize Legacy Applications and Systems?

Depending on your needs, you can choose the right option to revamp your legacy system. But in order for everything to go according to plan, you need to take certain steps.


🔹 Step 1: Search for reliable partners

Modernizing outdated systems is not a piece of cake and can definitely overwhelm many companies.

Perhaps you don’t know what kind of transformation to go for. Or you’re worried about modernization risks. Or maybe you just don’t know where to start and are looking for help with outdated legacy systems. Either way, partners like Inwedo are able to help you with the whole modernization project and will guide you through its maze. They know what approach legacy systems require and can choose the most effective ways to improve your old app and outdated business processes.

🔹 Step 2: Define your modernization goal

With the help of your new partner, clearly outline your modernization objectives and what you aim to achieve. This step will help you stay focused and measure the success of the modernization project.

🔹 Step 3: Analyze your legacy system

Conduct a comprehensive analysis of your existing legacy system. Maybe you just need to make minimal changes to the code? Or you must rewrite the app? This evaluation will guide your modernization strategy.

It’s best to begin with thorough workshops and system audits. Understand the existing foundation, pinpoint the strengths and weaknesses of the current system, and evaluate if the system’s goals align with your new visions.

🔹 Step 4: Choose the best modernization option and integrate systems

Based on your outcomes from analysis and defined goals, select the most effective way to modernize the legacy system. Then, integrate the modernized application with the actual systems. Usually, this involves creating robust interfaces or APIs that migrate data and communication between the modernized application and legacy systems.

Legacy Software Modernization Takeaways

Regardless of the chosen approach, you need to know that any system can transform into a legacy one if not properly maintained. So what should you do?

Understand essentials.

  • There isn’t a one-size-fits-all approach.
  • Transitioning is complex but manageable with the right strategy.

Navigate potential pitfalls.

  • Without a thorough assessment of the legacy system, you might miss critical components during the transition, and lead to disruptions.
  • Delaying modernization amplifies technical debt and future costs, so implement practices like static code analysis, unit testing, and continuous architectural review that prevent them and mitigate the necessity for a major overhaul down the road.
  • Anticipate the evolution of code dependencies – over time, these dependencies can become intricate and will lead to potential chaos when making changes.

Integration and interoperability.

  • Modernization isn’t just about adopting new tech but also ensuring seamless integration with existing systems.
  • Legacy system inflexibility can hinder integration. The chosen modernization method should promote interoperability.
  • Assure no loss of functionality or data.

A future-proof approach to modernization.

  • Look beyond the immediate challenges – choose strategies that offer the ability to adapt the new system to upcoming technological and business changes.
  • Continuously monitor the modernized system’s alignment with business goals.
  • Bet on regular maintenance.


Working on the legacy systems may be risky for the whole company. That’s why you must come out with a modernization initiative.

Choose the right approach, follow practical advice, and successfully modernize legacy software. Also, look for partners like Inwedo, who will collaborate closely with you and understand your unique needs and aspirations. Our expertise facilitates a smooth transition, and our mutual growth is the ultimate goal.

Contact us today or delve into our case studies to witness past success stories. Your transformation begins here.

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