AWS Certified Solutions Architect – Professional — Question 283

A financial company is using a high-performance compute cluster running on Amazon EC2 instances to perform market simulations. A DNS record must be created in an Amazon Route 53 private hosted zone when instances start. The DNS record must be removed after instances are terminated.
Currently the company uses a combination of Amazon CloudWatch Events and AWS Lambda to create the DNS record. The solution worked well in testing with small clusters, but in production with clusters containing thousands of instances the company sees the following error in the Lambda logs:
HTTP 400 error (Bad request).
The response header also includes a status code element with a value of `Throttling` and a status message element with a value of `Rate exceeded`.
Which combination of steps should the Solutions Architect take to resolve these issues? (Choose three.)

Answer options

• A. Configure an Amazon SOS FIFO queue and configure a CloudWatch Events rule to use this queue as a target. Remove the Lambda target from the CloudWatch Events rule.
• B. Configure an Amazon Kinesis data stream and configure a CloudWatch Events rule to use this queue as a target. Remove the Lambda target from the CloudWatch Events rule.
• C. Update the CloudWatch Events rule to trigger on Amazon EC2 ג€Instance Launch Successfulג€ and ג€Instance Terminate Successfulג€ events for the Auto Scaling group used by the cluster.
• D. Configure a Lambda function to retrieve messages from an Amazon SQS queue. Modify the Lambda function to retrieve a maximum of 10 messages then batch the messages by Amazon Route 53 API call type and submit. Delete the messages from the SQS queue after successful API calls.
• E. Configure an Amazon SQS standard queue and configure the existing CloudWatch Events rule to use this queue as a target. Remove the Lambda target from the CloudWatch Events rule.
• F. Configure a Lambda function to read data from the Amazon Kinesis data stream and configure the batch window to 5 minutes. Modify the function to make a single API call to Amazon Route 53 with all records read from the kinesis data stream.

Correct answer: A, C, D

Explanation

The API throttling error occurs because Route 53 rate limits are exceeded when thousands of EC2 instances simultaneously try to update DNS records. Using an Amazon SQS FIFO queue (A) buffers these requests and preserves the order of creation and deletion, while triggering the events from the Auto Scaling group (C) ensures accurate tracking of instance states. Finally, batching up to 10 DNS change operations into a single Route 53 API call using Lambda to poll the SQS queue (D) dramatically reduces the total number of API requests, staying well under the rate limits.