AWS Certified Solutions Architect – Professional — Question 425

A company has a web application that uses Amazon API Gateway, AWS Lambda, and Amazon DynamoDB. A recent marketing campaign has increased demand.
Monitoring software reports that many requests have significantly longer response times than before the marketing campaign.
A solutions architect enabled Amazon CloudWatch Logs for API Gateway and noticed that errors are occurring on 20% of the requests. In CloudWatch, the
Lambda function Throttles metric represents 1% of the requests and the Errors metric represents 10% of the requests. Application logs indicate that, when errors occur, there is a call to DynamoDB.
What change should the solutions architect make to improve the current response times as the web application becomes more popular?

Answer options

• A. Increase the concurrency limit of the Lambda function
• B. Implement DynamoDB auto scaling on the table
• C. Increase the API Gateway throttle limit
• D. Re-create the DynamoDB table with a better-partitioned primary index

Correct answer: B

Explanation

The application logs link the Lambda errors directly to DynamoDB calls, indicating that the database is throttled due to insufficient read/write capacity during peak traffic. Enabling DynamoDB auto scaling dynamically adjusts the table's provisioned throughput capacity to handle the increased load and eliminate these errors. Adjusting Lambda concurrency or API Gateway limits would not resolve the database bottleneck, and redesigning the partition key is an unnecessary and complex change for this capacity-related issue.