AWS Certified Solutions Architect – Professional — Question 656

A solutions architect is troubleshooting an application that runs on Amazon EC2 instances. The EC2 instances run in an Auto Scaling group. The application needs to access user data in an Amazon DynamoDB table that has fixed provisioned capacity.
To match the increased workload, the solutions architect recently doubled the maximum size of the Auto Scaling group. Now, when many instances launch at the same time, some application components are throttled when the components scan the DynamoDB table. The Auto Scaling group terminates the failing instances and starts new instances until all applications are running
A solutions architect must implement a solution to mitigate the throttling issue in the MOST cost-effective manner
Which solution will meet these requirements?

Answer options

• A. Double the provisioned read capacity of the DynamoDB table.
• B. Duplicate the DynamoDB table. Configure the running copy of the application to select at random which table it access.
• C. Set the DynamoDB table to on-demand mode.
• D. Add DynamoDB Accelerator (DAX) to the table.

Correct answer: C

Explanation

Switching the DynamoDB table to on-demand mode is the most cost-effective solution because it automatically scales to accommodate sudden spikes in traffic during instance launch sequences, and you only pay for the requests actually consumed. Keeping the table on provisioned capacity and doubling it (Option A) or adding a DynamoDB Accelerator (DAX) cluster (Option D) would result in high, continuous idle costs when the application is not actively scaling. Duplicating the table (Option B) introduces data consistency issues and unnecessary storage overhead without addressing the root scaling limitation.