AWS Certified Solutions Architect – Associate (SAA-C02) — Question 747

A manufacturing company has machine sensors that upload .csv files to an Amazon S3 bucket. These .csv files must be converted into images and must be made available as soon as possible for the automatic generation of graphical reports.
The images become irrelevant after 1 month, but the .csv files must be kept to train machine learning (ML) models twice a year. The ML trainings and audits are planned weeks in advance.
Which combination of steps will meet these requirements MOST cost-effectively? (Choose two.)

Answer options

• A. Launch an Amazon EC2 Spot Instance that downloads the .csv files every hour, generates the image files, and uploads the images to the S3 bucket.
• B. Design an AWS Lambda function that converts the .csv files into images and stores the images in the S3 bucket. Invoke the Lambda function when a .csv file is uploaded.
• C. Create S3 Lifecycle rules for .csv files and image files in the S3 bucket. Transition the .csv files from S3 Standard to S3 Glacier 1 day after they are uploaded. Expire the image files after 30 days.
• D. Create S3 Lifecycle rules for .csv files and image files in the S3 bucket. Transition the .csv files from S3 Standard to S3 One Zone-Infrequent Access (S3 One Zone-IA) 1 day after they are uploaded. Expire the image files after 30 days.
• E. Create S3 Lifecycle rules for .csv files and image files in the S3 bucket. Transition the .csv files from S3 Standard to S3 Standard-Infrequent Access (S3 Standard-IA) 1 day after they are uploaded. Keep the image files in Reduced Redundancy Storage (RRS).

Correct answer: B, C

Explanation

AWS Lambda (Option B) provides immediate, event-driven processing upon S3 upload, which is more cost-effective and faster than polling with an EC2 instance. S3 Glacier (Option C) is the most cost-effective storage class for the .csv files because they are only needed twice a year for pre-planned ML training, meaning the retrieval latency of Glacier is perfectly acceptable. Transitioning them to Glacier after 1 day and expiring the images after 30 days minimizes storage costs.