Why Core Systems Modernisation Is Challenging and Costs More Than Expected

The foundational core systems investment from the turn of the century has run its course for nearly every large organisation. 20+ years later, everyone is reaching the same conclusion:

Our core systems need to change.

The intent is right. The logic is compelling. The alternative of doing nothing poses unacceptable business continuity risks to the board. But the complexity and the cost are often underestimated.

Four Realities That Surface Quickly

In our 30+ years of practical experience delivering transformation and modernisation, the following realities tend to emerge:‍

1. The Business Case Is Harder Than It Looks

‍Before any transformation benefits appear, significant effort goes into rebuilding current functionality, integrations, and ways of working. The early value is stability and effectiveness — not change. Making a compelling business case for effectively investing to recreate what you already have is a tough one.

2. Cloud Migration Is Not an Upgrade

‍Modernising core systems in the cloud is not an upgrade, even if you stick with the same vendor. Architectures change. Data models evolve. Customisations behave differently or are no longer supported. Moving to cloud-based core platforms is a reimplementation that often requires significant infrastructure upgrades along the way.

3. Modern Platforms Won't Behave Like Legacy Systems

‍Over time, current platforms have been customised to support functions that may not exist in modern core systems. This can challenge long-standing practices that evolved in more flexible — but less disciplined — environments. Where legacy systems have been internally redeveloped, re-architecture of the enterprise systems landscape is almost certain to be required.

4. The Risk of Rebuilding the Past in New Technology

‍Under delivery pressure, tactical decisions accumulate. The result can be a modern platform that looks new but quietly carries much of yesterday's complexity forward.

The Real Opportunity

The real opportunity in core systems modernisation isn't technical. It's deciding strategically what the business architecture is going to be moving forward — taking into account the standards and capabilities of modern cloud platforms.

Mulberry Group works closely with CxOs to build smart business cases that drive pragmatic investment decisions in modernising core systems. To discuss your modernisation strategy, get in touch.

By Dimitrios Bairaktaris PhD | February 4, 2026

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