AWS Certified Solutions Architect – Professional — Question 946

A company runs a video processing platform. Files are uploaded by users who connect to a web server, which stores them on an Amazon EFS share. This web server is running on a single Amazon EC2 instance. A different group of instances, running in an Auto Scaling group, scans the EFS share directory structure for new files to process and generates new videos (thumbnails, different resolution, compression, etc.) according to the instructions file, which is uploaded along with the video files. A different application running on a group of instances managed by an Auto Scaling group processes the video files and then deletes them from the
EFS share. The results are stored in an S3 bucket. Links to the processed video files are emailed to the customer.
The company has recently discovered that as they add more instances to the Auto Scaling Group, many files are processed twice, so image processing speed is not improved. The maximum size of these video files is 2GB.
What should the Solutions Architect do to improve reliability and reduce the redundant processing of video files?

Answer options

• A. Modify the web application to upload the video files directly to Amazon S3. Use Amazon CloudWatch Events to trigger an AWS Lambda function every time a file is uploaded, and have this Lambda function put a message into an Amazon SQS queue. Modify the video processing application to read from SQS queue for new files and use the queue depth metric to scale instances in the video processing Auto Scaling group.
• B. Set up a cron job on the web server instance to synchronize the contents of the EFS share into Amazon S3. Trigger an AWS Lambda function every time a file is uploaded to process the video file and store the results in Amazon S3. Using Amazon CloudWatch Events, trigger an Amazon SES job to send an email to the customer containing the link to the processed file.
• C. Rewrite the web application to run directly from Amazon S3 and use Amazon API Gateway to upload the video files to an S3 bucket. Use an S3 trigger to run an AWS Lambda function each time a file is uploaded to process and store new video files in a different bucket. Using CloudWatch Events, trigger an SES job to send an email to the customer containing the link to the processed file.
• D. Rewrite the web application to run from Amazon S3 and upload the video files to an S3 bucket. Each time a new file is uploaded, trigger an AWS Lambda function to put a message in an SQS queue containing the link and the instructions. Modify the video processing application to read from the SQS queue and the S3 bucket. Use the queue depth metric to adjust the size of the Auto Scaling group for video processing instances.

Correct answer: B

Explanation

Synchronizing the EFS share to Amazon S3 via a cron job on the web server allows the system to transition to an event-driven architecture. Triggering an AWS Lambda function for each file uploaded to S3 ensures that each video is processed individually and exactly once, eliminating the race conditions caused by multiple EC2 instances scanning the same EFS directory. Finally, using Amazon CloudWatch Events to trigger Amazon SES ensures reliable delivery of the processed video links to customers.