Engineering for PSD3 and Open Finance: What Changes Technically

Regulation as an Engineering Driver 

PSD2 introduced APIs into banking. PSD3 and Open Finance extend that model significantly. The scope moves beyond payments into broader financial data sharing, tighter security requirements, and stronger control over customer consent. For engineering teams, this is not a regulatory update. It is a system-wide architectural shift. 

From a technical partner perspective, the challenge is clear: translate regulatory requirements into systems that are secure, scalable, and production-ready. 

From PSD2 to PSD3: What Actually Changes 

PSD3 builds on PSD2 but introduces stricter expectations in several areas: 

• stronger authentication and fraud prevention  
• improved API reliability and performance  
• clearer rules around access to financial data  
• expansion toward Open Finance (beyond payments)  

This shifts systems from “API exposure” to platform-level data sharing. From an engineering standpoint, APIs are no longer integration points. They become regulated products. 

API Architecture: From Exposure to Governance 

Under PSD3 and Open Finance, APIs must meet higher standards like consistent availability and performance SLAs , standardized data formats, strong versioning and backward compatibility. This requires moving from ad-hoc API layers to API governance frameworks. 

A production-ready architecture includes: 

• API gateways enforcing authentication and rate limiting  
• versioned API contracts aligned with regulatory requirements  
• monitoring for availability and response times  

From experience, the biggest gap in PSD2 implementations was not functionality. It was lack of consistency across APIs. PSD3 raises the bar by making this consistency mandatory. 

Consent Management as a Core System 

Consent becomes a central component in Open Finance. Systems must capture explicit user consent, define scope and duration of access, allow revocation at any time, and track consent usage across services. This introduces a new architectural capability: consent as a domain service. 

A typical flow: 

user-consent -> consent-service -> access-token -> data-access 

Consent is no longer a flag in a database. It becomes a first-class entity that governs all data access. A technical partner ensures that consent logic is centralized, auditable, enforced consistently across APIs.

Data Sharing Across Domains 

Open Finance extends beyond payments into areas such as: savings and investments, lending and credit data, insurance and financial products. This introduces some cross-domain data sharing challenges: 

different data models across systems  

varying data quality and formats  

multiple ownership boundaries  

Engineering systems must support domain-aligned APIs, standardized data contracts, transformation layers between systems. 

From a delivery perspective, this often requires introducing Anti-Corruption Layers to translate between legacy and modern domains. 

Security: Identity Over Perimeter 

PSD3 reinforces strong customer authentication and secure communication. Technically, this leads to: 

• identity-based access control  
• mutual TLS for service communication  
• token-based authorization (OAuth2 / OpenID Connect)  

Security shifts from network-level controls to identity-driven architectures. Every request must be authenticated, authorized, traceable. 

From experience, implementing this consistently across services is one of the most complex aspects of compliance. 

 

Observability and Regulatory Traceability 

PSD3 introduces stricter expectations around monitoring and reporting. Systems must provide: 

• detailed logs of API access  
• traceability of data usage  
• visibility into consent application  

This requires centralized logging, distributed tracing across services, audit-ready data pipelines.

A technical partner ensures that observability is built into the system, not added later. 

Performance and SLA Requirements 

Regulatory frameworks increasingly define expectations for API performance. This includes: 

response time limits  

availability thresholds  

fallback mechanisms  

Meeting these requirements brings on the need for a scalable infrastructure, caching strategies for high-frequency data, resilience patterns such as retries and circuit breakers. 

From experience, performance issues often appear under real load, not during testing. Designing for scale from the beginning is essential. 

Integrating with Legacy Systems 

Most banks do not start from a clean architecture. Legacy systems remain central to operations. PSD3 and Open Finance require exposing data from these systems without compromising stability. 

This is achieved through: 

API layers on top of legacy cores  

event-driven replication of data  

controlled access through integration services  

A technical partner ensures that integration does not create tight coupling or degrade performance.  

Governance and Change Management 

Regulated APIs evolve over time. New versions, new data fields, and updated requirements must be introduced without breaking existing integrations. 

This requires structured versioning strategies, backward-compatible changes, and controlled rollout processes. 

From a system perspective, governance becomes part of the architecture. 

The Role of a Technical Partner 

Delivering PSD3 and Open Finance capabilities requires coordination across: backend systems, API layers, security frameworks, data platforms. 

A technical partner contributes with key features by: 

• designing compliant architectures  
• implementing integration layers  
• ensuring consistency across services  
• supporting delivery in regulated environments  

The focus is not only on compliance. It is on building systems that remain scalable and maintainable beyond the initial implementation. 

Challenges and workarounds

Several challenges appear frequently in PSD3 initiatives: 

• treating consent as a simple data field  
• inconsistent API design across domains  
• weak observability and audit capabilities  
• underestimating integration complexity  

Addressing these early reduces risk and avoids rework. 

Compliance as a Platform Capability 

PSD3 and Open Finance redefine how banking systems expose and manage data. From an engineering perspective, this is not a set of isolated requirements. It is a shift toward platform-based architectures where APIs, consent, and data governance are core capabilities. 

A successful implementation depends on execution. Systems must be designed to handle regulatory requirements while remaining flexible and scalable. 

With the right architecture and delivery approach, compliance becomes more than an obligation. It becomes a foundation for building new financial services.