Healthcare integration engines such as Mirth Connect (NextGen Connect) are central to clinical interoperability, enabling the exchange of HL7, FHIR, and proprietary messages between disparate healthcare systems. A critical operational hazard arises when these engines invoke external third-party APIs that become slow, unresponsive, or permanently unavailable. Without explicit timeout controls, integration channels may block indefinitely, causing thread exhaustion, message backlog accumulation, degraded throughput, and complete engine unavailability—outcomes that directly threaten patient care continuity and regulatory compliance. This paper proposes a fault-tolerant timeout framework for external service calls in healthcare integration engines. The framework combines configurable connection and read timeouts, selective retry with exponential backoff, circuit breaker state management, and graceful fallback handling into a centralized invocation layer. Each component is governed by principles of deterministic termination, failure isolation, configurability, auditability, and clinical safety. Pseudocode algorithms are provided for each mechanism. Although implemented in the context of Mirth Connect, the architecture generalizes to other synchronous and asynchronous integration platforms. Evaluation demonstrates that the framework significantly reduces the risk of indefinite channel blocking while preserving message traceability, data integrity, and compliance with healthcare data governance requirements. 

healthcare integration engine, Mirth Connect, fault tolerance, timeout management, circuit breaker, retry policy, exponential backoff, graceful degradation, HL7, FHIR, API resilience, clinical interoperability

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