AWS Certified Advanced Networking – Specialty (ANS-C00) — Question 81

An organization is migrating its on-premises applications to AWS by using a lift-and-shift approach, taking advantage of managed AWS services wherever possible. The company must be able to edit the application code during the migration phase. One application is a traditional three-tier application, consisting of a web presentation tier, an application tier, and a database tier. The external calling client applications need their sessions to remain sticky to both the web and application nodes that they initially connect to.
Which load balancing solution would allow the web and application tiers to scale horizontally independent from one another other?

Answer options

• A. Use an Application Load Balancer at the web tier and a Classic Load Balancer at the application tier. Set session stickiness on both, but update the application code to create an application-controlled cookie on the Classic Load Balancer.
• B. Use an Application Load Balancer at both the web and application tiers, setting session stickiness at the target group level for both tiers.
• C. Deploy a web node and an application node as separate containers on the same host, using task linking to create a relationship between the pair. Add an Application Load Balancer with session stickiness in front of all web node containers.
• D. Use a Network Load Balancer at the web tier, and an Application Load Balancer at the application tier. Enable session stickiness on the Application Load Balancer, but take advantage of the native WebSockets protocols available to the Network Load Balancer.

Correct answer: B

Explanation

Option B is correct because using an Application Load Balancer at both tiers allows for independent scaling while also maintaining session stickiness at the target group level. Option A mixes load balancer types, which complicates the architecture unnecessarily. Option C does not provide the required scalability between the web and application layers since both are hosted together. Option D introduces a Network Load Balancer, which is not optimal for the application layer's requirements.