AWS Certified Solutions Architect – Associate (SAA-C02) — Question 659

A company has an application that gives users the ability to upload images to an Amazon S3 bucket. Each night, the company launches an Amazon EC2 Spot
Fleet that processes all the images that the company received that day. The code to process the images is small (less than 200 MB), and each image takes less than 5 minutes to process.
The company wants to change the application to process the images when the images are uploaded. However, the company is concerned about the cost of this new functionality.
What should a solutions architect do to implement this change MOST cost-effectively?

Answer options

• A. Use S3 events to invoke an AWS Lambda function to process the images.
• B. Use S3 events to launch an EC2 Reserved instance to process the images.
• C. Use S3 events to launch a container in AWS Fargate to process the images.
• D. Use S3 events to deploy an AWS Elastic Beanstalk application to process the images.

Correct answer: A

Explanation

AWS Lambda is the most cost-effective solution because it charges only for the actual compute time consumed, and the workload's resource constraints (under 200 MB code size and under 5 minutes execution time) easily fit within Lambda's limits. Triggering Lambda directly via Amazon S3 event notifications provides instantaneous, serverless scaling upon image upload. Other alternatives like EC2, AWS Fargate, and AWS Elastic Beanstalk introduce unnecessary operational overhead, slower startup times, and higher baseline costs for sporadic, event-driven tasks.