In the world of software development, Application Modernisation projects often start with a common scoping question: do we rewrite the whole system, or upgrade smaller targeted components over time?
While both approaches have merit, neither are perfect and the reality is often somewhere in between the two perspectives. But how can we make the right application modernisation decision?
Software Over Time
Most software systems start clean, well-structured, with technical features aligned to the business needs at the time, a smaller code base and less complexity.
However, as time passes, without continuous maintenance and observability to create awareness around key factors, and a clear scaling strategy to align runtime performance and cost with the application’s capabilities, clarity can quickly fade.
As the business drives new requirements, use cases and continuous innovation, new features are added and the functionality of the stack evolves and in certain scenarios a different architectural paradigm is also required, especially for increasingly complex scalability and high bandwidth needs.
Value of Software Maintenance and Support
Maintaining software ensures that digital solutions remain adaptable to change and align with evolving business goals. This requires dedication and strategic commitment. While these tasks enable innovation and allow for the technological edge to shine, many organisations perceive this work as a form of a support function rather than part of the core feature delivery stream.
As a result, they’re frequently deprioritised. Focus often falls onto new greener fields and arising topics or fruitful customer technical needs. The priority push is often feature development and not feature maintenance.
Over time, this neglect leads to system degradation and the silent build-up of technical debt. Often teams will not even question whether the right architecture was originally put in place for the technical goals. Code bases have dependencies to libraries and other internal projects. As the quantity of code increases horizontally so does the dependency depth, this creates a rigid and complex structure to manage, making core changes more difficult.
Modularity and abstraction can help navigate this complexity, but introducing more independent moving parts also increases the operational workload. It raises an important question of prioritisation: should teams invest in innovation, or focus on areas that directly support business continuity?
Even with modularity to enable smooth maintenance of outdated dependencies, like architecture, software libraries or infrastructure environments, support can still be time consuming and challenging.
The Threshold in Technical Debt
Over time, systems become increasingly fragile and outdated as complexity and dependencies increase, libraries become outdated or unsupported, application integration grows more complex and clear observability capability difficult to implement or maintain.
Often, the symptoms of technical debt appear when organisations find it hard to introduce change into their software. It is an unnecessarily difficult and complex task with many risks and unknown parameters involved.
But it is not only software which can stagnate, supporting environments and toolkits also need care, especially the technical and architectural documentation.
The danger is often when core modules become too risky to change. Infrastructure that once served the business needs well can become a constraint, especially without a scalable, forward-looking design in place to allow for the applications to cost effectively utilise it.
Eventually, the system hits a threshold—a point where small fixes no longer make sufficient difference and modernising aspects of the existing systems turns more into a complete overhaul and long-term project commitment.
Here, maintaining strategic vision and visibility over the organisation’s technology landscape is essential. It enables a more incremental, adaptive approach that evolves alongside emerging changes and business needs. However, once the critical threshold is passed, the question shifts—not whether modernisation is needed, but how broadly it should be applied and how those changes should be managed and delivered.
The Myth of the Perfect Solution
No modernisation effort starts with a clean slate. Legacy systems are often entangled with business logic, processes, and technical dependencies built over years of development and patching. While it may seem like a mess to untangle, the existing setup was built for a reason. There’s value in that history, and as improvements are made, it’s important not to lose sight of the core features or overlook existing technical constraints.
The volume of code, the depth of complexity and nested dependencies, the product vision of the existing features and the currently supported user base often require the process of modernisation to work in parallel to the ongoing workloads and systems.
So, is the answer to modernisation simply a matter of executing a large-scale rewrite to meet all the requirements at once? Or is it better to take a more incremental, agile approach—breaking the system down into smaller components and modernising piece by piece? The reality is, these two approaches are not mutually exclusive. In fact, the most successful modernisation efforts often blend elements of both.
A large-scale rewrite may be justified when the existing system is fundamentally misaligned with business goals or too fragile to evolve. In other cases, a modular, incremental strategy allows teams to deliver value continuously, reduce risk, and adapt more easily to changing priorities. The key lies in engineering a solution that fits the context—balancing technical feasibility, business urgency, and organisational capability.
Having the right approach for the right project matters. Some systems require surgical precision and gradual evolution, others need a bold reset.
Clear understanding of the current technical architecture and vision for the future is needed for the most cost effective and elegant solutions
Not sure if you need a full rewrite or just a smarter upgrade path?
Our Application Modernisation experts can help you assess your current architecture and define a tailored roadmap—whether that’s a clean-slate rebuild, incremental evolution, or a hybrid of both.