Controlled outbound integration to third parties via a central integration layer
The case study is based on an extensive integration project whose goal was to securely and consistently expose legacy systems to third parties through a central integration layer. The main focus was on analyzing existing services, managing integration logic, and validating API communication.
The organisation operated multiple internal legacy systems that needed to exchange data with external third parties. Direct outbound connectivity from individual systems was difficult to govern, audit and evolve, so a central integration layer became the controlled point for outbound communication.
Outbound integrations to third parties were inconsistent across internal systems. Security and transport requirements (e.g., mutual TLS and policy checks) varied by consumer, request transformations were duplicated, and there was no single place to validate requests and enforce contracts—leading to higher operational risk and poor auditability.
- Dependence on existing legacy systems
- Limited possibilities for changes in backend applications
- Regulatory and security requirements for communication with third parties
- Need to maintain operational continuity during integration
Responsible for analysing outbound integration scenarios, mapping internal data structures to partner contracts, and designing a controlled integration flow through the central integration layer. I also collaborated on workflow-based validation and decision logic (Camunda) to standardise request checks, transformations and error handling.
A central outbound integration pattern was designed where internal systems call the integration layer using an internal contract, the gateway enforces security and transport controls, and validation/orchestration logic is executed via workflow before communicating with the third party. Requests are transformed/enriched to the partner contract and responses are mapped back consistently to internal consumers, improving governance and auditability. The integration layer also standardised correlation IDs, audit logs and consistent error mapping so every outbound call is traceable end‑to‑end and incidents can be triaged quickly.
This sequence diagram illustrates the controlled outbound integration flow through a central API Gateway. Internal systems send requests via an internal contract, which undergo security validation, transformation, enrichment, and workflow-based validation (Camunda) before reaching the third-party system over mTLS. Responses follow the reverse path with consistent mapping back to internal consumers.
- Use a central integration layer as the single controlled outbound point to third parties
- Standardise security and transport controls (e.g., mTLS) at the gateway layer
- Implement validation and integration decision logic via workflow (Camunda) to keep rules auditable and maintainable
- Better interoperability between legacy and modern systems
- Better control over data and API contracts
- Reduced risks associated with direct integrations of legacy systems
- Greater transparency and auditability of integration flows
- Possibility of further expansion without interfering with core legacy applications
Technologies & Standards