Full replacement means a complete migration away from an existing core system, with the legacy platform retired once the transition is complete.

Unlike approaches that run a modern core alongside legacy technology, the destination is a fully modernised environment. That makes full replacement the highest-complexity of Mambu's five core transformation models.

Three things define the model:

The goal isn't to build new capabilities around the old core indefinitely. Products, data, integrations and operations need a clear path onto the new architecture so the legacy infrastructure can ultimately be retired.

Replacing a deeply embedded core can affect the wider banking ecosystem around it. Data, digital channels, reporting, third-party integrations and operational processes may all need to change alongside the core.

With more of the institution affected by the transformation, planning and executive oversight become critical. Clear sequencing, testing and governance help manage the complexity throughout migration.

The complexity is real, but OYAK ANKER Bank shows that it doesn't have to mean business disruption.

A full replacement might have a clear end state, but that doesn't mean every part of the transformation needs to change at the same moment.

Rigorous planning and phased execution can break the programme into manageable stages while keeping the final objective unchanged: complete migration away from legacy technology.

Institutions also need to think beyond simply replacing one core with another. Moving from an ageing monolith to a new monolith may solve today's problem without creating the flexibility needed for tomorrow.

A composable, API-first architecture takes a different approach. The core becomes part of a wider ecosystem of specialised capabilities connected through APIs, making it easier to evolve individual components as business and customer needs change.

OYAK ANKER Bank is a German commercial bank with roots stretching back to 1958. Operating exclusively through digital channels, it serves retail and corporate customers with products including savings accounts, fixed-term deposits, personal loans, trade finance, corporate banking and treasury management.

After decades of operation, its existing core banking system had reached its limits. The technology had become rigid, slow to adapt and costly to maintain, making it harder for the bank to respond to changing customer expectations, regulatory requirements and market demands.

But OYAK ANKER Bank didn't want to replace one ageing monolithic platform with another.

"We chose to start from a blank page and people only believed it when they saw the entire ecosystem working."

Dr Süleyman Erol, Managing Director at OYAK ANKER Bank

Working with Mambu and technology partner Innovance, the bank undertook a comprehensive full-stack modernisation, replacing its legacy systems with a cloud-native technology ecosystem built around Mambu's core banking platform.

The transformation went beyond the core. It included a new mobile banking platform, a reengineered data warehouse and cloud-native ecosystem applications, connected through a modern API-first architecture using microservices and event-driven workflows.

From initial planning and system design through to implementation and go-live, OYAK ANKER Bank completed the transition without business disruption.

With its core operations fully migrated to the cloud, the bank has launched deposit and lending solutions for individuals and businesses, including fixed-term deposits and personal loans. Its open architecture also connects with third-party systems including regulatory reporting, treasury management and mobile banking.

Working with Mambu and technology partner Innovance, the bank undertook a comprehensive full-stack modernisation, replacing its legacy systems with a cloud-native technology ecosystem built around Mambu's core banking platform.

The transformation went beyond the core. It included a new mobile banking platform, a reengineered data warehouse and cloud-native ecosystem applications, connected through a modern API-first architecture using microservices and event-driven workflows.

From initial planning and system design through to implementation and go-live, OYAK ANKER Bank completed the transition without business disruption.

With its core operations fully migrated to the cloud, the bank has launched deposit and lending solutions for individuals and businesses, including fixed-term deposits and personal loans. Its open architecture also connects with third-party systems including regulatory reporting, treasury management and mobile banking.

The OYAK ANKER Bank story illustrates an important distinction in full legacy replacement: complete transformation doesn't have to mean uncontrolled transformation.

The destination was comprehensive. All of the bank's legacy systems were replaced. But reaching that destination required planning the entire ecosystem, not simply swapping one core platform for another.

That means looking at how the core connects to digital channels, data, reporting and third-party services before migration begins. It also means designing the new architecture for change, so today's replacement doesn't become tomorrow's legacy constraint.