How do you implement the Saga pattern for distributed transactions across NestJS microservices?

Q: How do you implement the Saga pattern for distributed transactions across NestJS microservices?

// OrderService — reacts to payment events @EventPattern('payment_succeeded') async onPaymentSucceeded(@Payload() event: PaymentSucceededEvent): Promise { await this.ordersService.confirmOrder(event.orderId); this.client.emit('order_confirmed', { orderId: event.orderId }); } @EventPattern('payment_failed') async onPaymentFailed(@Payload() event: PaymentFailedEvent): Promise { await this.ordersService.cancelOrder(event.orderId); // compensating transaction this.client.emit('order_cancelled', { orderId: event.orderId }); } // InventoryService — reacts to order events @EventPattern('order_confirmed') async onOrderConfirmed(@Payload() event: OrderConfirmedEvent): Promise { await this.inventoryService.reserveItems(event.orderId); } @EventPattern('order_cancelled') async onOrderCancelled(@Payload() event: OrderCancelledEvent): Promise { await this.inventoryService.releaseReservation(event.orderId); // compensating } // Saga state — track progress for debugging @Entity('saga_state') export class SagaState { @PrimaryColumn() orderId: string; @Column() status: 'STARTED' | 'PAYMENT_PENDING' | 'CONFIRMED' | 'FAILED'; @Column('jsonb') history: SagaStep[]; } Choreography — each service publishes events and reacts to others; no central coordinator needed. Orchestration — a central Saga orchestrator sends commands and waits for replies; easier to visualize but creates coupling. Every step that can succeed must have a compensating transaction to undo it if a later step fails. Compensating transactions must also be idempotent — they may be called multiple times on redelivery. Store saga state in a database table for observability — distributed transaction failures are hard to debug without it.

Difficulty: 8/10

Saga orchestration, NestJS microservices, Compensating actions

Use choreography-based Sagas where each service reacts to domain events and emits compensating events on failure. Each service handles its own step and publishes the outcome. Compensating transactions undo completed steps when a later step fails. Track saga state in a database table for observability and debugging.

Choreography-based Saga with compensating transactions

Saga pattern design rules:

1
Choreography — each service publishes events and reacts to others; no central coordinator needed.

How do you implement the Saga pattern for distributed transactions across NestJS microservices?

Difficulty: 8/10

Saga orchestration, NestJS microservices, Compensating actions

Use choreography-based Sagas where each service reacts to domain events and emits compensating events on failure. Each service handles its own step and publishes the outcome. Compensating transactions undo completed steps when a later step fails. Track saga state in a database table for observability and debugging.

Choreography-based Saga with compensating transactions

Saga pattern design rules:

1
Choreography — each service publishes events and reacts to others; no central coordinator needed.

How do you implement the Saga pattern for distributed transactions across NestJS microservices?

How do you implement the Saga pattern for distributed transactions across NestJS microservices?

Scenario Questions

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