Saga Pattern: How Microservices Maintain Data Consistency Without ACID Transactions

In microservices architecture, each service owns its own database, making cross-service ACID transactions impossible — a problem the Saga pattern is designed to solve. The Saga pattern breaks a workflow into a sequence of local transactions, where each step triggers the next via events, and any failure triggers compensating transactions to undo prior steps. Two main approaches exist: Choreography, where services react to each other's events in a decentralized manner, and Orchestration, where a central coordinator directs each service and tracks overall saga state. Choreography offers loose coupling and horizontal scalability, while Orchestration provides clearer audit trails and easier debugging at the cost of a potential single point of failure. Key trade-offs of the Saga pattern include eventual consistency between steps, complex compensating logic, and the requirement that every step be idempotent to handle retries safely.