1. Introduction & The Problem: The Peril of Inconsistent State

In the world of microservices, decoupling services brings immense benefits in terms of scalability, agility, and independent deployment. However, this architectural choice introduces a formidable challenge: maintaining data consistency across multiple, independent databases when a single business operation spans several services. This is the problem of distributed transactions.

Traditionally, monolithic applications relied on two-phase commit (2PC) protocols for atomic operations across multiple resources. In a distributed microservice environment, 2PC is often impractical due to its blocking nature, high latency, and tight coupling between services, which directly contradicts the microservices philosophy. The alternative, simply letting services update their own data and hoping for the best, inevitably leads to data inconsistencies.…