AWS Certified Solutions Architect – Professional — Question 817

A bank is re-architecting its mainframe-based credit card approval processing application to a cloud-native application on the AWS cloud.
The new application will receive up to 1,000 requests per second at peak load. There are multiple steps to each transaction, and each step must receive the result of the previous step. The entire request must return an authorization response within less than 2 seconds with zero data loss. Every request must receive a response. The solution must be Payment Card Industry Data Security Standard (PCI DSS)-compliant.
Which option will meet all of the bank's objectives with the LEAST complexity and LOWEST cost while also meeting compliance requirements?

Answer options

• A. Create an Amazon API Gateway to process inbound requests using a single AWS Lambda task that performs multiple steps and returns a JSON object with the approval status. Open a support case to increase the limit for the number of concurrent Lambdas to allow room for bursts of activity due to the new application.
• B. Create an Application Load Balancer with an Amazon ECS cluster on Amazon EC2 Dedicated Instances in a target group to process incoming requests. Use Auto Scaling to scale the cluster out/in based on average CPU utilization. Deploy a web service that processes all of the approval steps and returns a JSON object with the approval status.
• C. Deploy the application on Amazon EC2 on Dedicated Instances. Use an Elastic Load Balancer in front of a farm of application servers in an Auto Scaling group to handle incoming requests. Scale out/in based on a custom Amazon CloudWatch metric for the number of inbound requests per second after measuring the capacity of a single instance.
• D. Create an Amazon API Gateway to process inbound requests using a series of AWS Lambda processes, each with an Amazon SQS input queue. As each step completes, it writes its result to the next step's queue. The final step returns a JSON object with the approval status. Open a support case to increase the limit for the number of concurrent Lambdas to allow room for bursts of activity due to the new application.

Correct answer: A

Explanation

Option A is correct because utilizing Amazon API Gateway and a single AWS Lambda function provides a highly cost-effective, serverless architecture that easily meets the 2-second latency requirement for sequential steps. Option D introduces excessive latency and complexity by chaining multiple SQS queues, which would make returning a synchronous response within 2 seconds highly impractical. Options B and C are incorrect because deploying dedicated EC2 instances dramatically increases both infrastructure costs and operational complexity compared to the serverless approach.