Series context (Part 4 of 8): This article assumes familiarity with ACID transactions and database concurrency. Understanding why consistency guarantees are hard at the database layer is essential context before introducing distributed patterns here.
Why Microservices in Banking?
Microservices in banking is the architectural pattern where a core banking system is broken into independently deployable, domain-owned services (CIF, Payments, Lending, Notifications) connected by an event bus instead of direct database calls. This replaces monolithic systems like T24 or Flexcube — where a single change to the Payments module requires redeploying the entire application and risks taking down unrelated services.
High-risk deployments: Modifying a small module requires redeploying the entire system. A patch to the Payments module can take down CIF.
Inefficient scaling: You cannot scale just the Payments module during peak loads without scaling everything else — including parts that don't need more capacity.
