International Research Journal of Engineering and Technology (IRJET)
e-ISSN: 2395-0056
Volume: 13 Issue: 01 | Jan 2026
p-ISSN: 2395-0072
www.irjet.net
From Monolith to Microservices: A Multivocal Literature Review of Zero-Downtime Migration Strategies in Fin tech Industry Thomas Paul1 1Senior Software Engineer, California, United States of America
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Abstract - Regulated industries such as finance are
processing requirements [4], [5]. Achieving near-continuous service during decomposition typically depends on incremental migration patterns that limit blast radius and enable reversible change. While industry practice often begins with interface-level replacement patterns, research emphasize that effective migration must address internal coupling, shared data dependencies, and operational constraints that persist beneath external APIs [6]. The data layer is repeatedly identified as the highest-risk component, particularly for enterprise-scale databases at terabyte to petabyte scale [7]. Change Data Capture (CDC) is widely used to replicate state transitions from the monolith to emerging services in near real time, supporting synchronization and continuity during transitional phases where multiple systems must operate in parallel [7]. Decentralized data management also introduces new challenges in transactional consistency. In strongly regulated transaction flows, strict coordination mechanisms remain common, and distributed commit approaches are frequently discussed as necessary for preserving atomicity across services [8]. For multiservice workflows, compensation-based patterns are often adopted, yet limitations such as insufficient isolation motivate enhanced coordination designs that constrain state transitions until workflow completion [9]. Additional approaches have reported improvements to integrity and latency by reducing abort frequency and constraining inconsistency windows [10]. Beyond correctness, continuous compliance requires end-to-end observability and auditability; event-driven approaches that maintain immutable records, combined with orchestration mechanisms for reporting and traceability, are frequently positioned as enablers of continuous regulatory alignment [8], [11]. Finally, long-term resilience in distributed architectures must address recovery complexity. While microservices can improve fault isolation, distributed persistence and heterogeneous storage complicate systemwide restoration and cross-service referential integrity [1]. Polyglot persistence and independent backup schedules can produce inconsistent recovery points across services, motivating recovery protocols that define and enforce a system-level consistency target during restoration [12]. Such mechanisms aim to minimize the interval of unrecoverable change and preserve cross-service referential correctness, which is critical for financial institutions operating under continuous service, mandates [12].
modernizing core platforms, but moving from monolithic systems to microservices introduces a critical challenge: how to migrate without interrupting mission critical operations. Regulated environments impose strict requirements for availability, data integrity, auditability, and compliance, which make conventional migration approaches that rely on downtime or temporary service degradation unsuitable. This study presents a multivocal literature review that synthesizes evidence from peer reviewed research and high relevance practitioner sources on strategies that enable continuous service during migration. Across the reviewed studies, recurring patterns include event driven integration, change data capture, coordinated dual write, progressive traffic shifting, and resilience controls such as circuit breakers and controlled failover, supported by observability and governance practices that preserve compliance during transitional states. A total of 109 records were screened across IEEE Xplore, ACM Digital Library, SpringerLink, arXiv, and Google Scholar, and four studies were selected for detailed analysis based on predefined criteria. The findings provide practical guidance for planning and executing live migrations in regulated and data intensive systems, and they highlight areas where additional empirical validation is needed.
Key Words: microservices, zero downtime migration, monolith to microservices, regulated systems, change data capture, event driven architecture, transactional consistency, compliance architecture
1. INTRODUCTION The transition from monolithic to microservices architectures in the financial sector is increasingly driven by the limitations of legacy platforms in meeting modern requirements for continuous availability, rapid change, and horizontal scalability [1]. Many core banking solutions still reflect product-centric designs that date back decades, and this structural rigidity complicates upgrades, increases operational risk, and makes outages especially costly in highdependency financial operations [2], [3]. Microservices are often adopted to reduce these risks through modularity and fault isolation while also supporting compliance obligations that demand traceability, controlled change, and operational resilience [1], [3]. However, zero-downtime migration in finance must preserve non-negotiable properties such as transactional integrity, low latency, and predictable performance, frequently requiring careful alignment with existing relational database constraints and real-time
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2. METHODOLOGY This study aims to systematically investigate architectural strategies, technical mechanisms, and operational
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