Zero-Downtime Migration Strategies for Decomposing Monoliths into Microservices in the Healthcare Industry: A Multivocal Literature Review

Healthcare organizations are modernizing core platforms such as electronic health records (EHRs), order-entry, and billing systems, but decomposing long-lived monoliths into microservices introduces a critical challenge: how to migrate without interrupting mission-critical care operations. Regulated healthcare environments impose strict requirements for availability, patient safety, privacy of protected health information (PHI), auditability, and compliance (e.g., HIPAA and GDPR), which makes conventional migration approaches that rely on downtime or temporary service degradation unsuitable. This study reports a multivocal literature review that synthesizes evidence from peer-reviewed research and high-relevance practitioner sources on strategies that enable continuous service during migration in healthcare settings. Across the reviewed studies, recurring patterns include event-driven integration, Change Data Capture (CDC), coordinated dual-write, backward-compatible schema evolution, progressive traffic shifting (canary and blue-green), and resilience controls such as circuit breakers, idempotent consumers, and controlled failover. These patterns are complemented by observability, governance, and security controls (encryption, access control, and immutable audit logs) that preserve compliance during transitional states. A total of 87 records were retrieved from IEEE Xplore, ACM Digital Library, and SpringerLink (Scopus and Web of Science returned zero records for the search string). After screening and full-text assessment using predefined criteria, a focused set of studies was selected for detailed synthesis. The findings provide practical guidance for planning and executing live migrations in regulated, data-intensive healthcare systems and highlight areas where additional empirical validation is needed.