AWS Certified Solutions Architect – Professional — Question 494

A solutions architect is evaluating the reliability of a recently migrated application running on AWS. The front end is hosted on Amazon S3 and accelerated by
Amazon CloudFront. The application layer is running in a stateless Docker container on an Amazon EC2 On-Demand Instance with an Elastic IP address. The storage layer is a MongoDB database running on an EC2 Reserved Instance in the same Availability Zone as the application layer.
Which combination of steps should the solutions architect take to eliminate single points of failure with minimal application code changes? (Choose two.)

Answer options

• A. Create a REST API in Amazon API Gateway and use AWS Lambda functions as the application layer
• B. Create an Application Load Balancer and migrate the Docker container to AWS Fargate
• C. Migrate the storage layer to Amazon DynamoDB
• D. Migrate the storage layer to Amazon DocumentDB (with MongoDB compatibility)
• E. Create an Application Load Balancer and move the storage layer to an EC2 Auto Scaling group

Correct answer: A, E

Explanation

Implementing Amazon API Gateway combined with AWS Lambda functions (Option A) eliminates the single point of failure at the application tier by replacing the single EC2 instance with a highly available, serverless architecture. Moving the database storage layer to an EC2 Auto Scaling group behind an Application Load Balancer (Option E) ensures the database instances can automatically recover and scale across multiple Availability Zones to prevent downtime. Other alternatives either introduce significant application code modifications or do not adequately resolve the single Availability Zone dependency for the database layer.