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How much are your old systems costing you?
For most organisations, it’s more than they realise, especially when you factor in the time, talent and costs to maintain it. Studies show that up to 80% of IT budgets are spent just keeping legacy systems running.
But replacing these systems can feel risky when they’re critical to your business. Pull the wrong thread, and everything could unravel.
So how do you modernise without putting your business at risk or creating tomorrow’s legacy system?
How to spot a legacy system before it breaks
A legacy system is any system that’s core to your business but no longer operates the way you need it to. That might be because it's expensive to run, difficult to maintain, or simply wasn’t built to adapt.
“These systems were built 15 or 20 years ago to give organisations a competitive edge, but they were never designed to grow with the business. Over time they’ve been patched onto and extended - like adding rooms to a house without thinking about the foundation. Eventually, the whole structure becomes unstable.”
George Lynch, Director of Technology and Solutions at NashTech.
There are clear signs that you have a legacy problem:
Four principles for successful legacy modernisation
The challenge is modernising your legacy system without disrupting the mission-critical operations it supports, (e.g. transactions, logistics, data processing, etc).
Here are four principles we’ve seen work in practice when it comes to modernising legacy systems.
1. Don’t just build for now. Build for what's likely to come next
Organisations often build systems to solve today’s problems and not tomorrows.
We’ve seen this happen many times. A business enters a new market and suddenly needs to process multi-currency transactions. But the systems weren’t designed for that. So, they patch it. Then patch the patch. Eventually, technology teams are left managing a messy, expensive patchwork that slows everything down.
You need to build modern systems that can grow with your business. That means creating IT infrastructure with flexibility and scalability in mind and understanding what innovation could look like in the future.
We often ask clients:
- What will your technology need to support in the next few years?
- Are you choosing platforms or systems that future teams will be able to maintain?
- Are there modern tools you want to integrate with the system?
- What’s the hidden cost of doing nothing?
Ruby on Rails, for example, was the go-to for web development. But now finding people with that skill set is tougher and more expensive. Choosing the wrong technology now can turn into a hiring and cost challenge later on.
2. Get clear on what legacy software is really costing you
Legacy IT issues often stay hidden until something breaks. A surge in users, new compliance rules, or entering new markets can quickly expose these systems as bottlenecks. By then, they’re already hitting customer experience, slowing you down, and impacting revenue.
Know what your legacy systems are costing you today and what they could cost tomorrow. What opportunities are you missing? Is your system blocking innovation, growth, or compliance?
This insight forms the foundation of your business case.
Make the risks clear across the organisation, framing modernisation as a smart and future-focused investment.
“When the system goes down, that’s when people realise they’ve been pushing their luck. Suddenly, risk becomes a business priority.”
George Lynch, Director of Technology and Solutions at NashTech
3. Make legacy modernisation a people-first transformation
Some organisations forget that legacy modernisation is also about people. These old systems have been around for years, sometimes decades. They’re embedded into how the business runs and how people work. For many teams, change doesn’t feel like progress. It feels personal.
“People are afraid of change. They know their current system, even if they don’t love it. It’s that old saying ‘better the devil you know’,” says George Lynch, Director of Technology and Solutions at NashTech.
Leading legacy modernisation with a strong change management strategy
Change needs to be led by the business, not just done to it.
“You can’t impose it on end users or leave it solely to the technology team. You need to involve the people who use and support the system every day, right from the start,” says George Lynch, Director of Technology and Solutions at NashTech.
Adopt agile practices to engage users early on, for example use show-and-tells to gather feedback and build buy-in. This helps users feel heard and invested in the final outcome.
Then, make sure training and knowledge transfer are in place for both end users and support teams.
When it’s time to go live, build internal momentum. Start with a team, product, or geography likely to accept change. If one team adopts the new system and prefers it, others will start saying, “why can’t we have that too?”.
That’s when transformation starts pulling people in instead of pushing them away.
“You’re trying to create demand for the change. That’s tough and it comes down to relentless communication. You have to keep engaging stakeholders at every level”.
George Lynch, Director of Technology and Solutions at NashTech.
4. Choose a modernisation approach that fits your business
There isn’t one clear approach to legacy modernisation. Your strategy depends on your budget, risk tolerance and how urgently you need to change.
Some organisations go for the “big bang” approach that replaces everything at once. While this can deliver fast results, it also comes with higher risk. Others prefer a gradual, iterative approach like the Strangler Fig Pattern, where legacy systems are replaced piece by piece. This lets the old and new systems coexist, often without users even noticing the transition.
A smart strategy balances speed, risk and keeping the business running smoothly.
For example, NashTech helped Lowell, a leading credit management company, to modernise their systems using the Strangler Fig Pattern. Instead of replacing everything at once, NashTech connected Lowell’s old systems to new ones using adapters. This allowed them to build new cloud-based platforms on Azure while still using their existing systems.
Over time, less important systems were replaced and core systems were integrated smoothly. This kept the business running without disruption.
GenAI for enabling legacy modernisation
There’s lots of debate about how AI might help bridge the legacy gap. Could AI transform outdated code into modern languages? Could it help automate the rebuilding process, or at least reduce time spent to do so?
Right now, AI isn’t there yet. NashTech’s own research has shown productivity gains when using generative AI for greenfield application development, but less benefits in brownfield or legacy modernisation projects.
But as AI gets better at recognising code patterns and refactoring them, using GenAI to accelerate legacy modernisation could be a possibility. It won’t replace developers, but it will help them work faster and smarter.
Get your modernisation project started today
Modernisation doesn’t have to be overwhelming. Whether you're starting with a legacy assessment or planning a full migration, our experts can help. Contact NashTech for a free consultation.
