SAGA Choreography vs Orchestration — which one should you choose?

Both implement the SAGA pattern but differ in who coordinates the workflow.

Choreography — event-driven, decentralized

Each service publishes events. Other services listen and react. No central coordinator.

// Order service
await _bus.PublishAsync(new OrderPlaced(orderId));   // and we're done

// Inventory service (separate codebase)
public async Task Handle(OrderPlaced ev) {
    await ReserveAsync(ev.OrderId);
    await _bus.PublishAsync(new StockReserved(ev.OrderId));
}

// Payment service (separate codebase)
public async Task Handle(StockReserved ev) { ... }

Orchestration — central coordinator

A dedicated orchestrator (often a state machine) sends commands and tracks state.

public class OrderSagaOrchestrator {
    public async Task RunAsync(PlaceOrder cmd) {
        await _inventory.ReserveAsync(cmd.OrderId, cmd.Items);
        try {
            await _payment.ChargeAsync(cmd.OrderId, cmd.Total);
            await _shipping.ScheduleAsync(cmd.OrderId);
        } catch {
            await _inventory.ReleaseAsync(cmd.OrderId, cmd.Items);
            throw;
        }
    }
}

Side-by-side

	Choreography	Orchestration
Workflow visibility	Low — distributed across N services	High — single state machine
Coupling	Loose (services know events)	Tighter (orchestrator knows everyone)
Tracing failures	Read N service logs	Read one timeline
Adding a step	Subscribe new service to existing events	Edit the state machine
Best for	2-3 step, stable workflows	4+ step, evolving workflows
Risk	Spaghetti at scale	Central bottleneck

Decision rule

Start with Choreography for 2-3 step workflows where the steps don't change often. Move to Orchestration the moment the workflow has 4+ steps OR business rules around the workflow change frequently.

Hybrid

In practice large systems use both:

• Choreography for fire-and-forget side effects (analytics, search indexing, notifications)
• Orchestration for the core business workflow (order, payment, fulfilment)

Tooling

• Choreography: Kafka, RabbitMQ, MassTransit
• Orchestration: Temporal.io, Camunda, MassTransit Saga, AWS Step Functions, Azure Durable Functions

For .NET specifically, MassTransit's saga state machine is the standard orchestration choice; for cross-language workflows, Temporal is the strongest option.