For some years now, we have been observing a significant rise in modernization initiatives for legacy software in German mid-sized companies. With rising maintenance costs, security gaps, and the skills shortage, the topic is increasingly moving into the foreground. This is precisely where well-founded modernization strategies for legacy software come into play, often referred to as the 7R framework. They help us renew old applications gradually or in a targeted manner, without endangering ongoing operations. Nadine Riederer, CEO of Avision, even emphasizes that software modernization has long ceased to be a purely technical update but is an important step toward future viability and innovation power for companies [1].

Before we decide whether to completely replace, migrate, or only selectively adapt our legacy software, we need to take a closer look at the respective approaches. According to Future Processing, there are seven central options for modernizing legacy systems: Retire, Retain, Relocate, Rehost, Replatform, Refactor, and Rearchitect [2]. Each of these strategies has different requirements, costs, and prospects of success. It is decisive not only to consider the technical state of the legacy system but also our business goals. Do we want to scale in the near future? Do we have to make our applications cloud-capable in order to integrate innovations such as AI or real-time analytics?

In our experience, modernization processes should always be planned holistically. A clear target picture, a concrete roadmap, and an open exchange between management, IT department, and business units are essential. It is also worth keeping the challenges that arise from the changeover in mind: such as the risk of system outages, possible data losses, or the resistance of those employees who are familiar with the old systems. We want to provide a structured overview of the seven strategies here and thus create a sound decision basis. Because the question is not whether we modernize, but how we most cleverly transform our existing legacy systems.

Retire Old Applications

The first option, Retire, describes shutting down or decommissioning applications that no longer have business value or whose operation is simply no longer worthwhile. Some legacy systems are barely used or have lost their functionality to other solutions. In such cases, switching them off can free up resources and reduce maintenance costs. According to Intertec, decommissioning unnecessary systems is part of a comprehensive modernization strategy, since it slims down the IT landscape and creates synergies (as of March 2026) [3].

However, we should carefully check in advance whether all the data and business processes coupled with the system are really covered. Sometimes such legacy systems guarantee an important archive function or provide legacy data for audits. A thoughtless shutdown can then bring legal or organizational problems. We therefore recommend defining the precise benefit of outdated applications and, if appropriate, integrating them into new systems before deciding on a final shutdown.

Retain Valuable Systems

The second option, Retain, means initially keeping certain parts of a legacy system and giving them prominence in our modernization program. Especially when individual applications map central core processes or other strategies would be too expensive, it can be sensible to consider retention. We thus avoid larger risks and preserve those functionalities that still work excellently or that have a high status in the company.

In the mid-market, we frequently encounter situations where very specific custom software — for example controlling unique production processes — is difficult to replace. An abrupt phase-out would cause unnecessary uncertainty here. In such cases, the application should be checked for compatibility and security but not pulled completely out of service. With contemporary protective measures and regular audits, the system remains stable until we plan a long-term modernization. At the same time, the Retain principle can pave the way for later partial modernizations as soon as resources are available or the pressure to switch increases.

Relocate to Other Environments

By Relocate, we mean moving an application into a more modern IT environment. Unlike Replatform or Rehost, the system is shifted to a new infrastructure or new data center without necessarily undergoing a deep transformation. To give an example: a historically grown application is moved out of an old corporate data center into a state-of-the-art external data center that has interfaces and security concepts at the latest standard.

This approach can simplify operations, especially when previous hosting is outdated or we are working at rigid capacity limits. Even so, we should consider that we modernize the application itself only minimally. We may still be tied to old technologies such as COBOL or Visual Basic [2]. Relocate can therefore be a first step for us to ensure stability before tackling more comprehensive modernizations. The important thing is to keep the future direction in view and plan strategically whether and when further steps follow.

Rehost via Lift and Shift

Rehost, often referred to as Lift and Shift, is a common approach for companies that want to quickly move their applications into a cloud environment. The code is hardly modified. We copy the existing application together with database and configuration into an IaaS or PaaS platform, which is helpful especially in situations where hardware has to be replaced quickly or modern scaling functions are needed. According to IBM, rehosting is an essential step for companies that want to migrate old mainframe applications to the cloud quickly to keep operations stable [4].

However, we should bear in mind with Rehost that any flaws in the code or architecture remain. In many cases, this approach does not lead to a reduction of technical debt. Instead, we simply shift the existing shortcomings into another environment. If we want to reduce technical debt, we should combine rehosting with further modernization steps in due course. The Rehost concept can, however, be a sensible interim step for gathering initial experience with cloud workloads or for solving urgent resource problems without endangering our core business.

Replatform onto New Platforms

With Replatform, we go a step further than with rehosting. We do lift the application into a new environment but make targeted changes to the code base or database design so that the software harmonizes optimally with the new platform. The focus is often on reducing existing dependencies and integrating cloud services such as serverless functions. Costs and complexity can thus be reduced by reshaping only those parts of the system that actually have to be adapted for cloud operation.

In our assessment, this approach offers a good middle ground between fundamental redevelopment and rapid migration. According to Intertec, effective modernization strategies for legacy software are not just cloud migrations but also include the integration of new technologies to ensure future viability [3]. If, for example, we split parts of a monolithic application into containerized microservices, the Replatform process can lay the groundwork for later expanding from monolith to microservices. However, we should also note that larger code changes are more demanding and the risk of errors can rise. Continuous quality assurance during the replatforming process is therefore mandatory.

Refactor for Improved Code

Refactor means that we improve the internal code structure of an application without fundamentally changing its core logic or its outward behavior. With this approach, we lower maintenance costs, reduce dependencies on outdated languages and frameworks, and at the same time create the basis for better scalability. Especially for systems that need to be regularly extended, clean code is decisive to facilitate future integrations and updates. The skills shortage in the area of older programming languages such as COBOL or Visual Basic can also become more severe the longer we keep the corresponding legacy technologies alive [2].

From our perspective, refactoring is particularly worthwhile for applications that we want to keep and continue to develop in the long term. We see a clear parallel here to the shortage of skilled workers for old technologies problem: as soon as a system uses common programming languages and modern frameworks, the dependency on rare specialists drops, which minimizes day-to-day risk. At the same time, a structured refactoring process helps to reduce technical debt by eliminating legacy assets such as inefficient code, unclear interfaces, and excessive complexity. Change management processes need to be designed cleanly so that we minimize downtime and errors here too.

Rearchitect Fundamental Structures

The most comprehensive approach among the 7R strategies is Rearchitect. Here, we redesign the architecture of an application completely from scratch, breaking up monolithic structures into microservices or integrating innovative technologies such as container orchestration. As part of this profound modernization, we already take scalability, fail-safety, and security aspects into account in the design, so that the software remains fit for the next 5 to 10 years. However, this step requires extensive planning, thorough testing, and close coordination of all parties. According to IBM, modernizing legacy applications always begins with a comprehensive evaluation of the existing application in order to clearly identify weaknesses and potential [4].

When we implement Rearchitect, we often use new technologies such as cloud-native services or containerized environments. We thus move away from rigid monolithic systems and lay the foundation for agile software development. The strangler fig pattern migration is often used here. New functionalities gradually grow around the legacy system until the old components are replaced step by step. We can thus ensure parallel operation and minimize the risk of major system outages. However, costs and time investment tend to be higher than with other strategies, so we have to weigh carefully whether such a major project corresponds to the expected business benefit.

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For better orientation, we have prepared a compact comparison of the seven modernization approaches. This table is intended to help weigh the different dimensions of cost, complexity, time horizon, and implementation risks.

| Strategy | Cost | Complexity | Time Horizon | Particularities | |---------------------------------------|-----------------|----------------|-----------------------|------------------------------------------------------------------| | Retire old applications | Low | Low | Short-term | Complete shutdown of dispensable components | | Retain valuable systems | Low to medium | Low to medium | Short to medium-term | Retention of strategically important core functions, less risk | | Relocate to other environments | Medium | Medium | Short to medium-term | Data center move without deep code adjustments | | Rehost via Lift and Shift | Medium | Medium | Short-term | Quick cloud move, but technical debt untouched | | Replatform onto new platforms | Medium-high | Medium-high | Medium-term | Partial rebuilding for cloud integration, reduces dependencies | | Refactor for improved code | Medium-high | Medium-high | Medium-term | Eliminates legacy code problems, reduces maintenance costs | | Rearchitect fundamental structures | High | High | Longer-term | Design of completely new architecture, highest flexibility |

This overview is, of course, a heavy simplification. In practice, every legacy system environment is unique, and there can also be hybrids of different strategies. But it shows fairly clearly in which environment which option is best deployed and where adjustments may be needed.

When Each Strategy Makes Sense

Decisive for choosing the right modernization strategy is, of course, our specific corporate context. If, for example, we are looking for immediate cost savings, Retire might offer a quick and simple answer. On the other hand, if we want to benefit quickly from innovative cloud technologies without overhauling every aspect of our legacy software, rehosting suggests itself. For particularly critical applications that are deeply integrated into our business processes, a step-by-step approach combining Retain elements with refactoring or replatforming is more suitable.

In many companies, the skills shortage also means that we cannot make big leaps. A staged concept is then conceivable, in which we first modernize legacy systems for partial processes to keep the infrastructure stable and spread risk. At the same time, we should consider early on whether the system should be operated in a cloud environment at all, or whether an on-premises solution with hybrid cloud approaches strategically fits better. A hybrid option does offer flexibility, but it also places high demands on data and identity management, as Talend emphasizes in the context of modern IT modernization [5].

Risks and Stumbling Blocks in Implementation

None of these seven approaches comes without potential pitfalls. Difficulties sometimes arise with data migration in legacy systems, since data formats and databases are often inadequately documented. A big bang vs. incremental migration conflict can also arise: if we switch everything at once, we save time but risk system outages. Or if we prefer to spread the migration over several phases, this increases security but can drag out the entire process.

Among the most common stumbling blocks are:

1. Missing discovery: If we know too little about dependencies in the legacy system at the outset, we quickly underestimate the effort.
2. Security gaps: With every change to the legacy system, we can create new attack vectors, so security must be considered from the beginning [4].
3. Unclear responsibilities: Large modernizations require clear roles so that project managers, application developers, and business units can cooperate efficiently.
4. Cultural hurdles: Employees who have worked with familiar workflows for years can have reservations about innovation. Transparent communication and a step-by-step introduction to new systems help here.

At the same time, a solid cost-benefit weighting is necessary. Each of these approaches can come with substantial budget and time investments. However, a successful modernization delivers considerable returns in the medium to long term. Companies can reduce maintenance costs of legacy systems, minimize downtime, and unlock new business opportunities. In the end, we have a strategic investment in the future viability of the entire company.

Influence on Employees and the Company

Good modernization initiatives recognize early that it is not just about technology but also about people. Many long-serving employees know their legacy applications inside out but may not want to dive into entirely new platforms or languages. Training and regular workshops break down fears of the unknown here. It is also sensible to identify internal "champions" who actively communicate the benefits of modern methods and provide help to other team members.

In the long run, this commitment pays off. We currently see frequently that companies not only modernize outdated software but also adapt their organizational processes at the same time. This leads to leaner workflows and increases innovation power. Especially when Rearchitect or Refactor are used, a new, more agile corporate culture often emerges that fosters learning processes and continuous improvement. In this process, a company can also better react to future technologies, such as AI-based analytics or automation systems.

Practical Tips for Getting Started

When dealing with modernization strategies for legacy software in practice, we should internalize the following ground rules as early as possible:

• We start with a thorough inventory of the current application landscape. This analysis provides information about redundancies, dependencies, and potential risks.
• We clarify security and compliance aspects at the beginning to forestall later surprises. Since B2B business often involves highly sensitive data, a strong focus must be placed on encryption, access control, and monitoring.
• We define measurable goals. Whether faster release cycles, fewer outages, or reduced license expenses — without concrete targets, it is difficult to assess the success of our modernization measure.
• We involve stakeholders from different business areas early on. Thanks to this holistic perspective, we recognize bottlenecks already in the planning phase and increase acceptance.

In parallel, we should consider whether to bring in external expertise. Especially in complex legacy environments, advice from service providers with extensive modernization experience is worthwhile. They can help us define realistic milestones and budgets. In the ideal case, close cooperation arises between internal and external teams so that the project is consistently driven forward.

Long-Term Perspective of Modernization

Beyond the immediate goal of making old systems faster, more secure, and more cost-effective, modernization pursues a more far-reaching vision: making our company fit for future challenges. In a time when technological leaps are the order of the day, innovations such as artificial intelligence, augmented reality, or big data can only be integrated on solid, future-proof technologies. Anyone operating with outdated software risks being left behind, so to speak, and losing customers to more agile competitors.

In addition, replacing legacy systems and substituting them with modern applications gives us enormous room for product development and customer service. Cloud-based systems enable rapid scaling, while microservices allow small functional building blocks to be dynamically swapped and updated. Once we use the advantages of a modular architecture, we can pilot new features within a few days and discontinue them as needed. Such agility can be a decisive competitive advantage that increases efficiency internally and ensures higher customer satisfaction externally.

Cost considerations also clearly speak for modernization projects: with contemporary solutions, we permanently lower our license and maintenance expenses and make it easier for us to attract new talent in the labor market or develop existing teams. Anyone who secures specialists for Java, C#, or modern web technologies invests in a competence base that is sustainably viable. Legacy software based on obscure languages can only be modernized with great effort and ties up bottleneck know-how that is barely available externally.

Conclusion

For us it is clear: each of these seven approaches offers a solid foundation for advancing the modernization of our legacy software. The choice of the right strategy is not a one-dimensional process, however, but a complex decision in which costs, risk, time, and corporate goals interact. While a simple Retire step conserves resources in the short term, a Rearchitect project can deliver the greatest benefit — albeit with greater effort.

From our perspective, modernization should always be viewed as a holistic project that not only replaces old technology but also creates room for organizational and cultural change. By exploring and understanding the different options (Retire, Retain, Relocate, Rehost, Replatform, Refactor, and Rearchitect), we can decide more precisely how we want to proceed. Modern IT architectures, higher data security, and increased innovation capability are tangible advantages that sustainably strengthen us in competition.

Wherever we stand — whether at the very beginning or already in the middle of initial migrations — our modernization strategies for legacy software are a key to staying competitive in the long term. With a clear roadmap, a thoughtful cost-benefit plan, and motivated teams, we create the necessary change. We are convinced: those who deal now with the right modernization options will soon benefit from optimized processes, a modern technology stack, and a working environment that is ready for the next innovation steps.