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DVA-C02 · Question #374

A developer is building an ecommerce application. When there is a sale event, the application needs to concurrently call three third-party systems to record the sale. The developer wrote three AWS Lam

The correct answer is B. Publish the sale event from the application to an Amazon Simple Notification Service (Amazon. Amazon SNS implements a fan-out pattern where a single published message is delivered independently to all subscribed endpoints simultaneously, making it ideal for triggering multiple Lambda functions concurrently.

Submitted by saadiq_pk· Mar 5, 2026Development with AWS Services

Question

A developer is building an ecommerce application. When there is a sale event, the application needs to concurrently call three third-party systems to record the sale. The developer wrote three AWS Lambda functions. There is one Lambda function for each third-party system, which contains complex integration logic. These Lambda functions are all independent. The developer needs to design the application so each Lambda function will run regardless of others' success or failure. Which solution will meet these requirements?

Options

  • APublish the sale event from the application to an Amazon Simple Queue Service (Amazon SQS)
  • BPublish the sale event from the application to an Amazon Simple Notification Service (Amazon
  • CPublish the sale event from the application to an Application Load Balancer (ALB). Add the three
  • DPublish the sale event from the application to an AWS Step Functions state machine. Move the

How the community answered

(54 responses)
  • A
    13% (7)
  • B
    78% (42)
  • C
    2% (1)
  • D
    7% (4)

Why each option

Amazon SNS implements a fan-out pattern where a single published message is delivered independently to all subscribed endpoints simultaneously, making it ideal for triggering multiple Lambda functions concurrently.

APublish the sale event from the application to an Amazon Simple Queue Service (Amazon SQS)

SQS is a point-to-point queue; each message is consumed by only one consumer, so a single SQS queue cannot fan-out the same message to three different Lambda functions simultaneously.

BPublish the sale event from the application to an Amazon Simple Notification Service (AmazonCorrect

When the sale event is published to an SNS topic with all three Lambda functions subscribed, SNS delivers the message to each subscription independently and concurrently. Each Lambda function is invoked regardless of the others' success or failure because SNS manages delivery to each subscriber separately.

CPublish the sale event from the application to an Application Load Balancer (ALB). Add the three

An Application Load Balancer routes a request to a single target based on rules; it does not broadcast the same event to multiple Lambda targets concurrently.

DPublish the sale event from the application to an AWS Step Functions state machine. Move the

AWS Step Functions orchestrates sequential or parallel workflows with dependency management, which adds unnecessary complexity for a simple independent fan-out pattern.

Concept tested: SNS fan-out pattern for concurrent Lambda invocations

Source: https://docs.aws.amazon.com/sns/latest/dg/sns-common-scenarios.html

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