Background
European Bank had a strong core banking and card issuance business but no way to offer point-of-sale installment financing a product increasingly expected by retail partners and younger customers who were defaulting to third-party BNPL providers for checkout financing instead of using European Bank’s own credit products. Merchant partners were asking for a “Pay in 4” or short-term installment option they could offer directly at checkout, and European Bank risked losing both transaction volume and the customer relationship to standalone BNPL players.
European Bank engaged us to design and build a BNPL capability that could plug into its existing core banking and card systems rather than being bolted on as a disconnected third-party integration.
Research & Discovery
Audited European Bank’s existing credit decisioning and card authorization systems to identify what could be reused versus what needed to be built new
Interviewed merchant partners to understand checkout integration requirements (API-first, low-latency approval, minimal friction)
Reviewed regulatory requirements for short-term consumer credit disclosures in European Bank’s operating markets
Benchmarked existing BNPL providers (approval flow, repayment scheduling, default handling) to identify table-stakes features versus differentiators
Mapped the full customer journey from checkout financing offer through repayment and potential default, identifying where friction or drop-off was most likely
Underwriting & Risk Engine Design
Designed a real-time underwriting engine capable of returning an approval decision in under 2 seconds at checkout
Built a rules-based pre-qualification layer using existing Bank customer data (account history, existing credit relationship) to fast-track approvals for known customers
Integrated a third-party bureau data feed for new-to-bank applicants, with a fallback decisioning path if the external service was unavailable
Established configurable risk tiers so European Bank’s risk team could adjust approval thresholds without requiring an engineering release
Built a repayment scheduling engine supporting multiple installment structures (Pay in 4, 3-month, 6-month) with configurable interest/fee rules per tier
Development & Infrastructure Integration
Built the BNPL decisioning and origination service as a set of independently deployable microservices, connected via Kafka to European Bank’s core ledger for real-time balance and repayment posting
Exposed a merchant-facing REST API for checkout integration, with a GraphQL layer for European Bank’s internal servicing and collections tools
Implemented idempotent transaction handling to prevent duplicate loan originations under retry conditions at checkout
Containerized all services with Docker and deployed on Kubernetes, allowing the underwriting engine to scale independently during peak retail periods (e.g., holiday shopping)
Set up a dedicated reconciliation pipeline to match BNPL originations and repayments against the core ledger nightly, flagging discrepancies for the operations team
Technical Challenges & How We Solved Them
Sub-2-second approval SLA Early underwriting prototypes took 6–8 seconds when synchronously calling the bureau data service. We solved this by pre-fetching risk signals for known customers ahead of checkout and running new-applicant bureau calls in parallel with rules-engine pre-qualification, collapsing the critical path to under 1.5 seconds on average.
Ledger consistency under high concurrency Multiple simultaneous checkout originations risked race conditions against the core ledger. We introduced Kafka-based event ordering per customer account and idempotency keys per transaction to guarantee exactly-once posting.
Merchant integration friction Smaller merchant partners lacked engineering resources for a full API integration. We built a hosted checkout widget (embeddable via a single script tag) as a lower-friction alternative to the raw API, which most smaller merchants adopted instead.
Regulatory disclosure requirements varying by market Repayment terms and required disclosures differed across European Bank’s operating regions. We built a configurable disclosure and terms template engine so compliance could update language per jurisdiction without an engineering change.
Key Features
Instant Checkout Financing real-time approval and financing offer presented directly at the point of sale, with no redirect to a third-party site.
Configurable Risk Tiers risk team can adjust approval thresholds and interest/fee structures without code changes.
Hosted Checkout Widget a drop-in embeddable financing widget for merchants without dedicated API integration resources.
Automated Repayment Scheduling supports multiple installment structures with automated reminders and retry logic for missed payments.
Real-Time Ledger Posting BNPL originations and repayments post directly to European Bank’s core ledger, eliminating manual reconciliation.
Merchant & Servicing Dashboards internal tools for European Bank’s collections and merchant-support teams to view originations, repayment status, and flagged accounts.
Impact
The BNPL product allowed European Bank to retain checkout financing volume that was previously flowing to third-party providers, while keeping the full customer credit relationship in-house. The sub-2-second approval flow reduced checkout abandonment compared to European Bank’s earlier manual credit application process, and the configurable risk-tier system let the risk team respond to portfolio performance without waiting on engineering cycles.
Outcomes:
Checkout approval decisions returned in under 2 seconds on average
BNPL originations reconciled automatically against the core ledger, removing a previously manual nightly process
Merchant onboarding time reduced significantly via the hosted checkout widget compared to full API integration
Risk team gained self-service control over approval thresholds and pricing tiers
Platform scaled cleanly through a peak seasonal retail period without manual intervention
Client Feedback
“We’d been watching transaction volume leak to BNPL competitors for two years. Having our own financing product one that actually talks to our core ledger in real time instead of sitting on top of it changed the conversation with our merchant partners completely.”
Head of Consumer Lending, European Bank
Conclusion
By building BNPL capability as a natively integrated extension of European Bank’s core banking and risk infrastructure rather than a bolted-on third-party product, European Bank was able to offer competitive point-of-sale financing while retaining full ownership of the underwriting, servicing, and customer relationship. The modular, event-driven architecture also gives European Bank a foundation to extend into adjacent lending products in the future.
