Saga

A Saga is a pattern for executing a business transaction that spans multiple services or databases by chaining local transactions together, with compensating actions to roll back partial progress on failure. Sagas replace distributed transactions (two-phase commit) in microservice systems where global ACID across services is impractical.

How it works

A saga breaks a business transaction into a sequence of steps. Each step is a local transaction in one service. If any step fails, the saga runs compensating actions for all previously-completed steps to undo their effects. The saga ends when either all steps succeed or all compensations have run.

Two coordination styles

• Choreography. Services react to events from other services; no central coordinator. Easier to start, harder to reason about as the saga grows.
• Orchestration. A central saga orchestrator (a workflow engine or service) drives the sequence and decides what to do next. Easier to observe, debug, and modify; introduces one component that must be highly available.

Common workflow engines

• Temporal, Cadence, AWS Step Functions, Camunda, Conductor, Azure Durable Functions, Restate