For 70 years, BankB has focused on building a distinctive position as Belgium’s complementary option for customers who want to save or need credit. With ambitions to grow while preserving its specialist model, BankB chose Mambu to modernise its banking infrastructure, combining a cloud-native core and centralised payments, including Swift connectivity.
BankB
BankB is an independent Belgian bank, specialising in savings and lending for private and professional customers, with lending activity in Belgium and France and savings distributed across selected European markets. Founded in 1956 as Centrale Kredietverlening (CKV Bank), it has built its proposition around finding tailored solutions for customers whose financing needs may not always fit the standard model of larger financial institutions.
As Belgium’s smallest bank, BankB deliberately positions itself as a complementary banking partner rather than a traditional primary bank, managing total assets of approximately €1.76 billion.
Its model is strongly intermediary-led, with a network of more than 500 savings agents and credit brokers supporting customers across its savings and lending business. BankB also extends its savings reach beyond Belgium through Raisin, giving savers in markets including Germany, the Netherlands and Spain access to selected BankB savings products.
To support its growth while preserving the flexibility at the heart of its business model, BankB also needed to modernise its technology.
Its existing core banking environment was highly integrated and monolithic. As the underlying technology aged, introducing change became increasingly complex and operational risk increased. BankB needed an architecture that could respond more quickly to changing customer, business and regulatory requirements while supporting its specialist approach to lending.
The bank wanted to move towards a cloud-based, API-first model architecture with limited customisation inside the core. Specialist applications and BankB-developed microservices could then provide the functionality required around it, allowing the bank to modernise progressively rather than replace one tightly coupled environment with another.
Payments presented an additional challenge. BankB had historically used KBC as sponsor bank for its deposits business, while lending payments were handled separately. As the bank looked to grow, it wanted to bring payments together through one central gateway and one sponsor bank, while adding SEPA Direct Debit to its lending proposition for the first time.
Achieving that with the existing technology would have required point-to-point Swift connections across different legacy systems and servicing banks. BankB considered that approach too complex and operationally risky. Moving to ING, which could support the bank across its payment needs, created the opportunity to simplify that setup while maintaining reliable mortgage disbursements and borrower repayments.
BankB selected Mambu’s cloud-native core banking platform in 2024 as part of a dual-core transformation strategy. The programme initially focused on mortgage lending, with the longer-term ambition of progressively replacing BankB’s legacy core and extending the new architecture across its wider product portfolio.
Mambu’s SaaS model and composable architecture aligned with BankB’s approach. Rather than heavily customising the core, BankB could use Mambu as its banking engine while connecting its own microservices, specialist applications and other technology through APIs.
In 2025, the relationship expanded into payments. BankB selected Mambu Payments and its Swift Business Connect solution to support its connectivity with ING, Direct Debit mandate management and integrate closely lending and payment flows.
Through Mambu Payments, BankB can now centralise its bank payments through one gateway rather than managing individual connectivity independently. Swift Business Connect provides fully managed access to Swift through Alliance Cloud, with Mambu managing the underlying infrastructure, security and connectivity requirements and ING serving as BankB’s SEPA sponsor bank.
“Connecting to Swift through Mambu's Alliance Cloud connectivity allows us to centralise all our bank payments via one gateway, serviced through our SEPA sponsor bank relationship with ING. The implementation with Mambu Payments was done quickly and reliably. Payment operations on Mambu's platform are more streamlined and efficient, and enable us to better serve our customers.”
- Patrick Herwegh, CIO at BankB
BankB approached the transformation in phases rather than attempting to replace its existing banking environment in one step.
The first production milestone came through payments. Mambu Payments went live first, allowing BankB to move its SEPA payment flows through Swift connectivity to ING while maintaining the processes its lending business depends on.
The next milestone followed soon after with its lending offering. After an 18-month implementation, BankB launched its term mortgage loan offering on Mambu, integrated with the nCino loan origination system already used by the bank. The wider implementation required significant integration work across BankB’s existing systems, newly developed applications and third-party technology. BankB connected these through its API-based data integration layer, alongside platforms including OutSystems and Exact. It also leveraged Amazon Web Services (AWS) cloud capabilities to support its security requirements.
The programme required significant integration work and close coordination across BankB and the Mambu teams. As the project progressed, the Mambu team adapted the implementation approach to BankB’s specific operating model and lean internal teams, supported by regular steering meetings between the organisations involved. The experience gained has also created a stronger foundation for BankB’s next phases of transformation.
BankB is now live across both Mambu Core and Mambu Payments, marking two significant steps in its move away from a tightly-coupled legacy environment.
Through Mambu Payments, BankB has centralised its SEPA payment connectivity through a single gateway, with ING as its sponsor bank.The bank currently processes around 4,500 SEPA Credit Transfer transactions each month through the platform, supporting payment flows including mortgage disbursements to notaries. The setup also adds SEPA Direct Debit to BankB’s lending proposition, addressing a capability gap the bank had previously identified as a competitive disadvantage.
On the core side, BankB’s mortgage product powered by Mambu’s lending engine gives the bank a production foundation from which to progressively move more lending activity and its existing loan portfolio onto the new architecture.
These milestones form part of a much broader growth plan. BankB aims to increase annual new mortgage lending by 67%, from €300 million to €500 million by 2030, supported by investment in its technology architecture, people and distribution network.
BankB is also looking at how the new architecture can support its growing use of AI. The bank is already developing AI agents, including for loan document recognition. Mambu’s Model Context Protocol (MCP) solution can now seamlessly connect the bank’s models and agents to the core.
The longer-term roadmap will also bring BankB’s savings products and services onto Mambu, followed by further online banking capabilities. As more of the business moves onto the new architecture, BankB plans to reduce its reliance on legacy technology and create a more consistent foundation across lending, savings and payments.
“We are still at the beginning of our transformation with Mambu, but we now have the foundation in place to progressively migrate our lending portfolio and expand our product offering. The goal is a more flexible banking architecture that can support BankB’s growth over the long term.”
- Patrick Herwegh, CIO at BankB
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