AWS Certified DevOps Engineer – Professional (DOP-C02) — Question 325

A company is building a serverless application that uses AWS Lambda functions to process data.

A BeginResponse Lambda function initializes data in response to specific application events. The company needs to ensure that a large number of Lambda functions are invoked after the BeginResponse Lambda function runs. Each Lambda function must be invoked in parallel and depends on only the outputs of the BeginResponse Lambda function. Each Lambda function has retry logic for invocation and must be able to fine-tune concurrency without losing data.

Which solution will meet these requirements with the MOST operational efficiency?

Answer options

• A. Create an Amazon Simple Notification Service (Amazon SNS) topic. Modify the BeginResponse Lambda function to publish to the SNS topic before the BeginResponse Lambda function finishes running. Subscribe all Lambda functions that need to invoke after the BeginResponse Lambda function runs to the SNS topic. Subscribe any new Lambda functions to the SNS topic.
• B. Create an Amazon Simple Queue Service (Amazon SQS) queue for each Lambda function that needs to run after the BeginResponse Lambda function runs. Subscribe each Lambda function to its own SQS queue. Create an Amazon Simple Notification Service (Amazon SNS) topic. Subscribe each SQS queue to the SNS topic. Modify the BeginResponse function to publish to the SNS topic when it finishes running.
• C. Create an Amazon Simple Queue Service (Amazon SQS) queue for each Lambda function that needs to run after the BeginResponse Lambda function runs. Subscribe the Lambda function to the SQS queue. Create an Amazon Simple Notification Service (Amazon SNS) topic for each SQS queue. Subscribe the SQS queues to the SNS topics. Modify the BeginResponse function to publish to the SNS topics when the function finishes running.
• D. Create an AWS Step Functions Standard Workflow. Configure states in the workflow to invoke the Lambda functions sequentially. Create an Amazon Simple Notification Service (Amazon SNS) topic. Modify the BeginResponse Lambda function to publish to the SNS topic before the Lambda function finishes running. Create a new Lambda function that is subscribed to the SNS topic and that invokes the Step Functions workflow.

Correct answer: B

Explanation

Using an SNS-to-SQS fan-out pattern allows the BeginResponse Lambda function to publish a message once, which is then parallelized to multiple SQS queues. Because each downstream Lambda function is triggered by its own SQS queue, you can easily control individual concurrency levels and manage retries without risking message loss. Direct SNS subscriptions lack queuing features, while creating an SNS topic per queue or using sequential Step Functions adds unnecessary operational overhead and fails to meet parallel execution requirements.