Senior API Integration Lead / Integration Architect

ASO Systems is seeking an experienced Senior API Integration Lead / Integration Architect to lead the development, implementation, and testing of integrations between a core enterprise software platform, independent applications, and external payment and identity providers. The ideal candidate will have strong hands-on experience building reliable APIs, structured-file integrations, and secure data exchanges across independently managed systems. This role requires active engineering involvement, technical leadership, troubleshooting, and coordination of end-to-end integration testing with internal teams and external providers. Key Responsibilities • Lead the design, development, and implementation of APIs and structured-file integrations between enterprise applications. • Develop and maintain secure REST APIs, data exchange interfaces, and third-party system integrations. • Define API contracts, data schemas, version control, validation rules, and integration standards. • Implement authentication, authorization, and caller-specific access permissions. • Develop reliable retry mechanisms, error handling, duplicate prevention, and reconciliation processes. • Manage corrected messages, file reprocessing, failed transactions, and data consistency across systems. • Coordinate integration activities with external vendors, payment providers, identity platforms, and independent application teams. • Lead sandbox onboarding, interface validation, and joint integration testing. • Troubleshoot complex integration failures using logs, transaction records, and evidence from connected systems. • Support payment, refund, settlement, identity, learning, certification, and event-data integrations as applicable. • Coordinate principal event and learning system joint testing beginning in July 2027. • Support production readiness, cutover, post-deployment troubleshooting, and interface confirmation. Required Qualifications • 7+ years of software integration, API development, or systems integration experience preferred. • Mandatory: Proven hands-on experience delivering production API and structured-file integrations across independently owned systems. • Strong experience with REST APIs, JSON, XML, and structured data exchanges. • Experience with API schema management, versioning, validation, and backward compatibility. • Strong understanding of API authentication, authorization, and secure system-to-system communication. • Experience implementing retries, idempotency, error recovery, duplicate prevention, and transaction reconciliation. • Proven ability to investigate and resolve complex production integration failures. • Experience coordinating and completing end-to-end integration testing with multiple independent system owners. • Ability to demonstrate successful joint testing supported by evidence from both connected systems. • Strong technical communication, troubleshooting, and cross-functional coordination skills. • Availability for integration development, testing, production cutover, and post-launch support. • Ability to maintain reliable working-hour overlap with European and Korean teams. Preferred Skills • C# / .NET / ASP.NET Core • REST APIs / OpenAPI / Swagger • JSON Schema / XML / XSD • PostgreSQL / SQL Server • API Gateway and Integration Middleware • OAuth 2.0 / OpenID Connect • Payment Gateway Integration • Payment, Refund, and Split-Settlement Reconciliation • Identity Provider Integration • Webhooks / Provider Callbacks • Event-Driven Architecture • Message Queues / RabbitMQ / Kafka • File Processing / SFTP • Data Mapping and Transformation • Automated API and Integration Testing • Postman / Newman • CI/CD and DevOps • AWS / Cloud Integration • Learning Management Systems / Certification Platforms • Event Management Systems Please provide: Your RESUME highlighting production API and systems integration projects.