The uncomfortable truth about legacy systems

Mitchell: If launching even a small feature requires a steering committee, then it's not the regulation that's slowing you down. It's design debt, or as we call it a complexity tax. All institutions must adapt to shifting markets and regulations, but competitive banks invest in systems that make rapid change possible.

Jorno: The tipping point for change rarely happens because of one event. Leaders eventually see that legacy systems are more than costly, they are barriers to competitiveness. When you are spending 70-80% of the IT budget on just “keeping the lights on,” then you don't have room for innovation. While you’re stuck with slow fixes, new rivals are moving at lightning speed. Eventually, if you can't meet customer needs, you become irrelevant.

The shift to composable and the immediate impact

Mitchell: Composable banking only works when the whole architecture moves together, not as a set of separate boxes. In this setup, you are only as fast as the slowest dependency – whether that may be core, payments, cards, onboarding, or KYC. That reality pushes a different way of working: shorter cycles, shared ownership across teams, and a mindset that’s comfortable solving end-to-end problems across the stack, not just within a single system.

Jorno: Most banks are familiar with composability in theory, but true transformation begins with pragmatic steps: starting small, proving value fast, then scaling up. Our guidance is designed to help financial institutions begin with specific use cases like using a dual-core where legacy and new systems run in parallel. This enables banks to innovate safely and migrate away from legacy step by step.

The most underrated benefits: autonomy, speed and scale

Mitchell: Mambu empowers lean teams to ship products in days without large-scale re-platforming or code rewrites. The result is a level of autonomy and nimbleness that surprises many clients.

For example, BUUT, an ABN AMRO venture, launched a bank for young customers in just a year with a full suite of products.

Flowe successfully shifted from a challenger bank to Payments-as-a-Service in six months, leveraging Mambu's core.

From established banks to small institutions, customers configure products and respond to change without heavy technical lift.

Jorno: It is natural to be cautious when migrating millions of transactions or complex business accounts to the cloud. One Northern European bank questioned whether Mambu could manage sophisticated interest calculations and handle large-scale data migration. After thorough technical validation, the institution now operates one of the region’s most agile, modern business account systems, which proves Mambu’s scalability and reliability for top-tier banks.

Innovation and compliance

Mitchell: Innovation cannot come at the expense of compliance. Mambu embeds compliance controls and audit trails directly in workflows, supporting real-time risk management. The platform enables new product launches in weeks, ensuring banks do not trade speed for safety.

The foundation of partnership: transparency and maturity

Mitchell: Our approach from the start is transparent, and goes beyond mapping roles in the IT landscape. We are clear on where Mambu is most valuable, where partners deliver value, and where trade-offs sit ahead. We also challenge early when we see unrealistic expectations, unnecessary complexity, or trade-offs ahead, because surprises are expensive in core transformations. This honesty is central to building trust and continues during the entirety of our relationship. When friction arises, we address and resolve it collaboratively.

Jorno: Mambu’s expertise and maturity in composable banking is the main reason clients choose us. As core transformation becomes a greater priority, banks compare architectural strategies: modular versus fully composable. We demonstrate both the advantages of composable banking and Mambu’s position as the most proven composable core, supported by the largest base of live customers and partners globally.

This track record gives decision-makers the confidence they need. Many recall past failures in core banking projects, but Mambu’s incremental, low-risk methodology offers a practical path forward.

Success measured together

Mitchell: Success with Mambu is created together. We align early on what outcomes matter most for each customer – speed of change, operational efficiency, scalability, or enabling new products and markets. From there, we measure and refine progress, remove blockers, and create joint milestones as the business evolves. When meaningful milestones are achieved, we make them visible and celebrate them with the customer, because transformation is built on stacked successes, not on one go-live moment.

Looking ahead

Mitchell: Composable banking is becoming the default for both financial and non-financial institutions that want to launch future-proof, adaptable financial products quickly. To do that well, they need an architecture that is robust and stays flexible over time, without creating new complexity. Mambu’s advantage is 15 years of delivering this in production, across markets and customer types.

Jorno: Over the years, institutions have come to see Mambu as the core banking of choice to legacy providers. As new banks launch and established institutions renew their infrastructure, Mambu remains the reference point for modern, composable core banking globally. Mambu’s position is clear. We are defining the next generation of banking.