AWS Certified Solutions Architect – Associate (SAA-C03) — Question 1013

A solutions architect is creating an application that will handle batch processing of large amounts of data. The input data will be held in Amazon S3 and the output data will be stored in a different S3 bucket. For processing, the application will transfer the data over the network between multiple Amazon EC2 instances.

What should the solutions architect do to reduce the overall data transfer costs?

Answer options

• A. Place all the EC2 instances in an Auto Scaling group.
• B. Place all the EC2 instances in the same AWS Region.
• C. Place all the EC2 instances in the same Availability Zone.
• D. Place all the EC2 instances in private subnets in multiple Availability Zones.

Correct answer: C

Explanation

Data transfer between Amazon EC2 instances in the same Availability Zone using private IP addresses is free, which minimizes network costs for inter-node communication. Placing instances in the same AWS Region but across different Availability Zones (Option B and Option D) still incurs data transfer charges when data crosses AZ boundaries. Using an Auto Scaling group (Option A) manages instance capacity but does not inherently eliminate cross-AZ data transfer fees.