Summary
Key results
Functional migration concept enabling platform validation and a phased migration plan
Lower maintenance costs and full feature continuity
Modernizing a payment platform without risking business continuity
Worldline decided to replace its existing Java-based payment platform with a modern .NET microservices architecture to support further development and long-term scalability. The platform had reliably served key business customers for years, but its technology lifecycle made it increasingly difficult and costly to maintain.
The modernization effort went beyond a technical upgrade. Many customers relied on a broad set of payment functionalities tightly integrated into their daily operations, including:
- Token-based payments
- Recurring payment scenarios
- Enterprise-level security mechanisms aligned with Payment Card Industry Data Security Standard (PCI-DSS) requirements
Preserving these capabilities during the transition was essential to ensure a smooth migration.
To manage the complexity of the transition and reduce risk, Worldline set a clear goal: to build a Minimum Viable Product (MVP) that would demonstrate a practical migration path to the new platform.
The MVP was designed to:
- Integrate with the legacy system
- Replicate critical functionalities in the new .NET environment
- Validate the target architecture under real operational conditions
- Provide a foundation for planning a phased migration of key customers
- Enable further development on the new platform
Given the long-term cooperation between the two companies, Worldline chose Sii to support the platform modernization initiative. Since 2020, Sii Poland has been working closely with Worldline to deliver digital payment solutions for demanding e-commerce environments, building a partnership based on shared goals, trust, and deep understanding of the payments domain. This collaboration created a solid basis for addressing complex platform modernization challenges while maintaining a strong focus on reliability, scalability, and real business needs.
„Our relationship has been really great. It’s more of a partnership rather than contract and supplier type of relationship.” – Ana Milosevic, VP of Product & Tech, Worldline
A structured approach to platform modernization
Sii experts worked closely with Worldline’s architects over the course of four months to design and implement a migration concept that enabled a controlled transition from the legacy payment platform to a modern .NET microservices-based solution.
The scope of work included:
- Analysis of business requirements, legacy architecture, and merchant-used features
- Identification and replication of key payment functionalities in a .NET-based microservices environment
- Design of the migration concept, along with solution documentation and use cases
- Development of an MVP integrating the legacy and new platforms
- Preparation of test scenarios and implementation of automated tests using Playwright and xUnit
- Execution of a pilot end-to-end implementation of the solution
- Validation of solution performance based on metric analysis
Long-term platform readiness with no compromise on functionality
The migration concept and MVP delivered by Sii enabled Worldline to modernize its payment platform while preserving all capabilities already used by key customers. By maintaining full feature continuity during the transition from Java to .NET, Worldline could move forward with confidence, without disrupting existing payment scenarios.
The MVP provided Worldline with a fully functional product that could be presented internally and to customers, making it possible to define a clear and realistic migration schedule to the new platform. This approach reduced risk, supported informed decision-making, and created space for further improvements as the platform evolves.
At the same time, consolidating the technology stack around .NET reduced long-term maintenance effort and simplified further development. The new solution also expanded functional flexibility by enabling reusable payment tokens for applications beyond payment initiation, supporting Card-on-File and recurring payment scenarios. Advanced card data tokenization aligned with Payment Card Industry Data Security Standard (PCI-DSS) requirements strengthened security and compliance for enterprise customers.
As a result, Worldline gained a validated platform setup that supports both stable operations today and the gradual rollout of new payment capabilities in the future.
Key results
- Functional MVP supporting validation of the target platform and definition of a phased migration schedule
- Continuity of all key payment functionalities during the transition from Java to .NET
- Reduced long-term maintenance costs through consolidation to a single .NET-based technology stack
- Reusable payment tokens enabling applications beyond payment initiation
- Support for Card-on-File and recurring payment scenarios
- Advanced card data tokenization aligned with PCI-DSS requirements