AWS Certified Solutions Architect – Professional — Question 302

A company is running a two-tier web-based application in an on-premises data center. The application user consists of a single server running a stateful application. The application connects to a PostgreSQL database running on a separate server. The application's user base is expected to grow significantly, so the company is migrating the application and database to AWS. The solution will use Amazon Aurora PostgreSQL, Amazon EC2 Auto Scaling, and Elastic Load
Balancing.
Which solution will provide a consistent user experience that will allow the application and database tiers to scale?

Answer options

• A. Enable Aurora Auto Scaling for Aurora Replicas. Use a Network Load Balancer with the least outstanding requests routing algorithm and sticky sessions enabled.
• B. Enable Aurora Auto Scaling for Aurora writes. Use an Application Load Balancer with the round robin routing algorithm and sticky sessions enabled.
• C. Enable Aurora Auto Scaling for Aurora Replicas. Use an Application Load Balancer with the robin routing and sticky sessions enabled.
• D. Enable Aurora Scaling for Aurora writers. Use a Network Load Balancer with the least outstanding requests routing algorithm and sticky sessions enabled.

Correct answer: B

Explanation

Option B is correct because the stateful nature of the application requires sticky sessions to ensure users are consistently routed to the same backend server, a feature natively supported by the Application Load Balancer (ALB) using the round robin algorithm. Additionally, configuring Aurora Auto Scaling ensures that the database tier can dynamically scale to handle the increased load. Network Load Balancers do not support HTTP-level sticky sessions in the same manner as Application Load Balancers, making options A and D incorrect.