We see again and again how outdated software severely limits innovation capability and competitiveness in the German mid-market. Especially when core processes are run by a legacy system, it becomes challenging to adapt to new market demands. That is why the all-important question for many IT leaders and managing directors is: when should we replace our legacy system? In practice, the warning signs accumulate to the point where they are hard to ignore. Not only does the risk of outages rise, but also the pressure from high maintenance costs, security gaps, and the growing shortage of skilled workers who still master older technologies.

The need for modernization is often recognized too late. Many companies rely on the same system for years — a system that has stood the test of time but is steadily losing flexibility. Sudden compatibility issues, regulatory requirements, or missing cloud interfaces can then only be worked around at great expense. This not only causes stress and higher IT costs, but above all hinders the development of the business model. Competitors who have long since modernized their software landscape can react faster to customer and market needs.

We understand that a replacement does not have to happen overnight. A planned, gradual transition is often the better strategy, for instance via the strangler fig pattern migration or other hybrid approaches. As several industry reports show, modernization can even be designed in such a way that the existing infrastructure largely remains and new functionality is integrated step by step [1]. Even so, there are clear warning signs that the time has come to replace or at least significantly modernize a legacy system. Below, we present ten typical indicators where we recommend taking a closer look and developing a concrete roadmap for replacement.

Warning Sign 1: Rising Maintenance Costs

A first clear indication is a rapid rise in maintenance and operating costs. If we notice that resources keep flowing into the upkeep of legacy systems instead of into innovative projects, caution is warranted. These expenses not only consume the IT budget but also reduce the company's agility. Many firms invest up to 80% of their IT budget in legacy systems instead of using it for contemporary technologies [2].

The reasons usually lie in expensive custom adaptations or in dependence on third-party providers who charge high fees for support. On top of this come costs for outdated hardware, licensing fees, and external consultants who have to provide the necessary know-how. In this way, an avalanche of costs builds up that keeps growing without us drawing significant value from the system.

To counter this, we advise taking stock promptly and initiating clear modernization measures. Even a meaningful business case can show what long-term savings are possible through a new, more efficient system [2]. The point is not just immediate savings, but also unused opportunities for growth and innovation. Anyone who ignores this warning light ends up paying twice: directly through high maintenance costs and indirectly through missed revenue. A next step could be to deliberately examine strategies for reducing maintenance costs of legacy systems.

Warning Sign 2: Growing Security Risks

With every passing year, the risk increases that a legacy system will exhibit security vulnerabilities. Often the manufacturer's official support comes to an end. Security updates are no longer provided, and the system no longer meets current compliance requirements. Especially in regulated industries, a missed security update can quickly have costly consequences, ranging from substantial penalties to loss of customer trust [2].

We advise checking regularly whether all security standards and encryption procedures are up to date. For example, encrypted communication protocols such as OSDP and hardware with secure elements are used today to prevent tampering [1]. Legacy systems often no longer meet these basic requirements. The resulting security gaps represent a significant entry point into the entire corporate IT.

So if you repeatedly struggle with malware attacks, system crashes, or unauthorized access to sensitive data, it is time to act decisively. In many cases, superficial "patching" is not enough to remain secure long-term. We therefore recommend integrating new security concepts as part of a modernization project and designing the system in such a way that future updates can be applied without difficulty.

Warning Sign 3: Skills Shortage Escalates

Outdated technologies often work only with very specific know-how. Either employees who maintain the legacy system are close to retirement, or the corresponding developers and administrators are hard to find on the market. We see in practice again and again that companies become extremely dependent on the departure of a single expert because that person is the only one who really understands the legacy system inside and out.

On the one hand, this personnel situation leads to bottlenecks in maintenance. On the other hand, costs rise when external specialists for outdated programming languages have to be hired. The problem is exacerbated by the fact that young IT professionals usually prefer to work with modern tech stacks. Anyone who can offer them only COBOL, Visual Basic, or old database structures faces major difficulties in recruiting.

As soon as we notice that our teams want to expand but can hardly find candidates for the existing technologies, it is time to replace the legacy system. In doing so, we actively counter the shortage of skilled workers for legacy technologies and at the same time create room for new competencies that serve our company in the long term. Studies also show that modernization increases employer attractiveness and reduces turnover.

Warning Sign 4: High Technical Debt

Technical debt arises when adjustments and extensions are made to a legacy system over years without structurally modernizing the overall system. In many companies, entire layers of stopgap fixes, poorly documented interfaces, and unofficial workarounds exist. This leads to complex, hard-to-maintain code that becomes even more vulnerable with every additional change.

This construct can work in the short term, but in the long term it blocks our development. New requirements can only be implemented with great effort, frequent code refactoring is necessary, and the danger of unintended side effects rises. Since documentation in legacy software is often incomplete, internal and external teams find it difficult to keep an overview. Here, too, the rule applies: every new function or correction costs more time and money than necessary.

To pay down this "debt," it makes sense to start a fundamental replacement or modernization. In the course of the project, for example, we can bring the software architecture up to current standards and at the same time reduce technical debt. In addition, a thorough analysis can help to identify and eliminate redundant modules in the long term [3]. Anyone who is still hesitating should bear in mind that every day with high technical debt further increases the risk of system errors and security gaps.

Warning Sign 5: Overly Rigid System Architecture

In the past, it was common to develop monolithic software. From today's perspective, these systems often appear rigid because individual components are tightly intertwined. New features can only be integrated into the core with great difficulty, which slows innovation. On top of that, service orientation — for example microservices — cannot be implemented in legacy systems, or only rudimentarily.

We frequently find that rigid monoliths cannot integrate state-of-the-art cloud services or AI modules without major rework. This has direct consequences for our competitiveness: while agile competitors quickly test and deploy new tools, we struggle with complex interface problems. An outdated design means that we want to react to important trends, but the legacy system does not support this.

Anyone who has reached this point should look more closely at how to convert from a monolith to microservices or what a gradual transition to a more flexible architecture might look like. Platforms with open architecture and cloud or hybrid deployment options in particular are considered essential for keeping pace with technical progress in 2024 and beyond [1]. A rigid system architecture is therefore a clear warning sign that we should consider a replacement process.

Warning Sign 6: Complicated Data Migration

A reliable indicator of outdated software is the effort we have to put into data migration every single time. Perhaps a great deal of data still resides locally in Access databases or in proprietary formats that are difficult to import into modern BI or ERP systems. Reports and analyses then require manual exports and imports, which is not only time-consuming but also increases the risk of errors.

In some cases, the data itself is inconsistent or has duplicates and gaps because no robust data management strategy is in place. This makes all business processes — from purchasing and production through to customer service — more vulnerable to misinformation. As a result, you constantly paddle along with workarounds instead of sustainably improving data integration.

Anyone permanently stuck in this migration holding pattern should look into a strategic approach to data migration in legacy systems. Many companies report that only after replacing their legacy system were they able to build a reliable and automated data foundation [4]. This in turn lays the basis for modern technologies such as predictive analytics or AI-supported decision-making. So if data migrations regularly cause headaches, a replacement — or at the very least a comprehensive modernization — is advisable.

Warning Sign 7: Tangled Legacy Landscape

Often there is not just one legacy system, but several that have grown over the years. In different departments and regions, isolated solutions have established themselves that hardly fit together. This creates overlaps, duplicate data structures, and complicated interfaces that can only be maintained at great expense.

We see that in such landscapes, the view of the bigger picture usually gets lost. Each area optimizes its own solution instead of pulling together. This heterogeneity hampers digital transformation initiatives because it is almost impossible to introduce a central platform or smoothly integrate new services. Often we hear sentences like "We've always done it this way," which in the long run stifles the spirit of innovation.

Especially when we notice that the legacy systems hinder cross-departmental cooperation and team spirit, it is time to consolidate them. A concept for modernizing legacy systems generally includes a unified data and process landscape. Anyone who tackles this transition consistently gains not only technical efficiency but also clear responsibilities, better communication, and more room to grow.

Warning Sign 8: Missing Modernization Strategy

A clear indication that a legacy system is long overdue is also the fact that there is no clear strategy for its further development. While we usually draw up a roadmap for new systems, legacy software often lacks both a timeline and investment planning for modernization phases. As a result, only spot updates are applied when something acutely fails or security gaps appear.

This "firefighting mentality" costs us more in the long run than if we worked on a comprehensive roadmap early on. Without a clear goal or guiding principle, resources and budgets are often used inefficiently. This can mean having to live with outdated functionality and losing competitiveness in core areas.

We therefore advise developing a structured concept that takes the entire lifecycle into account. This is where concepts such as modernization strategies for legacy software come into play, allowing us to proceed step by step but sustainably. According to experts, the key lies in clear operational goals, interdisciplinary planning, and embedding a culture that views digital transformation as an ongoing process [1].

Warning Sign 9: Rigid Migration Approaches

Even if we are already considering a replacement or modernization, a misguided migration approach can become a stumbling block. Anyone who insists strictly on a "Big Bang" instead of integrating systems step by step accepts high risks. We know cases in which a migration project failed massively because the entire switch was supposed to take place at once and brought all processes to a halt.

A significantly less risky alternative is incremental or stepwise migration. Companies can run new and old systems in parallel temporarily, perform tests in smaller increments, and gradually stabilize interfaces. In addition, technical debt can be reduced bit by bit without endangering ongoing operations. This is in line with the approach of taking a close look at the big bang vs. incremental migration debate and, if appropriate, choosing a strangler fig pattern migration to disentangle legacy applications.

So if we sense that a planned switch is supposed to happen in a single feat of strength while important risk factors are overlooked, that is a warning sign. Experience — as bbv.ch consistently advises — calls for early analysis, close coordination between departments, and realistic time buffers. Only this way can scope creep be avoided and a controlled modernization be enforced.

Warning Sign 10: Holding Back Business Strategy

Finally, the clearest warning sign is that the legacy system blocks central business initiatives. Perhaps we are planning to offer cloud-based services or to test new digital business models. But the old gets in the way of the new: our product range cannot scale, customer data cannot be linked, and automation is only possible to a limited extent.

This blockage sometimes manifests subtly in our shelving of ideas or starting projects half-heartedly. But it can also happen that we leave large revenue potentials on the table because our infrastructure is simply not ready to map new processes. Especially in times when digital transformation is indispensable, this hesitation can cost us our market position.

We therefore recommend taking a close look at whether the legacy system is preventing us from pursuing innovation or cooperating flexibly with partners. If the prerequisites are not met, you should quickly replace the legacy system — or at the very least define a target architecture that gradually integrates all relevant business processes. This frees us from old shackles and creates room for long-term growth.

Conclusion: Act in Time Instead of Waiting

Anyone who recognizes themselves in several of these warning signs should not lose any time. Legacy software may have worked for a long time, but in today's dynamic market environment, relying solely on the tried and true is risky. High maintenance costs, growing security gaps, personnel bottlenecks, and the lack of support for modern technologies speak a clear language. At the latest, when the legacy system blocks strategically important projects, action is unavoidable.

In our experience, replacement is not a sudden tour de force, but rather a planned path that we have to design with care. Alongside the choice of suitable methods — such as a sustainable modernization strategy for legacy software or a phase-in-phase-out solution — what is needed is professional change management. Only when management, business units, and IT pull together can resistance be reduced and all potential lifted.

In many cases, it is worth taking a close look at hybrid concepts that gradually decouple and replace a legacy system. Anyone who pushes their cloud integration cleverly benefits more quickly from AI-supported analytics, automated processes, and current security standards. Lastly, it is crucial that we continually examine whether our IT landscape can adapt to new conditions and growth plans. That is precisely what sustainable modernization means: away from rigid legacy assets, toward a forward-looking architecture that allows us more flexibility, innovation, and productivity.

It is therefore advisable to start an inventory now, to check the existing systems for their suitability, and to identify the point at which modernization becomes inevitable. If you find that several or even all of the ten warning signs above apply, you have probably been overdue for a replacement for some time. Our recommendation: take the first step, bring all relevant stakeholders on board, and develop a roadmap. A modern IT foundation is the basis for sustainable growth and lasting success — and that is exactly what we all want to ensure.