Context

While working at Form3, a cloud-native payment infrastructure provider, I contributed to the SEPA Instant payment rail integration with RT1, operated by EBA Clearing.

Form3 provides a unified API layer that allows banks and financial institutions to send and receive payments without directly managing scheme connectivity or data center infrastructure. Behind that abstraction lies complex, highly regulated, real-time financial message processing.

I worked on the integration layer responsible for transforming internal API requests into ISO 20022 pacs messages compliant with RT1 specifications.

Challenge

SEPA Instant payments operate under strict real-time constraints and zero tolerance for financial ambiguity.

Key challenges included:

• Accurate ISO 20022 pacs message generation and validation
• Strict scheme compliance with RT1 requirements
• Deterministic idempotent processing
• Safe retry mechanisms without risk of duplicate settlement
• Real-time SLA constraints
• Full traceability and auditability of every transaction
• Production reliability under continuous load

In financial infrastructure, if something fails, you must know exactly what happened to the money, immediately and conclusively.

What I Did

• Implemented message transformation logic from internal unified API models into ISO 20022 pacs messages
• Ensured strict schema validation and conformance to RT1 specifications
• Designed and maintained idempotent processing flows to guarantee safe replays
• Implemented robust retry logic aligned with financial consistency rules
• Contributed to timeout handling and scheme error mapping back to API consumers
• Strengthened observability to ensure every transaction state was fully traceable
• Maintained 100% automated test coverage for critical financial logic
• Participated in on-call rotations, incident resolution, and production debugging
• Investigated and resolved payment processing edge cases under live conditions
• Contributed to performance improvements ensuring stable real-time processing

Impact

• Helped enable real-time money transfers between banks across Europe, where payments are completed in seconds instead of hours or days
• Allowed financial institutions to integrate with the SEPA Instant network through a single API, removing the need to build and maintain complex payment infrastructure
• Ensured that every transaction could be fully traced and explained, which is critical when handling real customer money
• Contributed to a highly reliable payment system where downtime or errors are simply not acceptable
• Helped financial institutions adopt instant payments faster without building their own scheme connectivity