AWS Certified Solutions Architect Associate SAA-C03 Practice Question
An organization requires a mechanism to distribute web traffic across multiple EC2 instances to ensure high availability and fault tolerance for its online shopping platform. The web application needs to support the WebSocket protocol and maintain HTTP-cookie-based sticky sessions so that users always reach the same backend instance during a session. Which AWS service should be used to meet these specific requirements?
The Application Load Balancer (ALB) is the only Elastic Load Balancing option that offers all of the needed features in one service:
Layer-7 (HTTP/HTTPS) support that allows an HTTP/1.1 Upgrade to WebSocket (ws/wss) - native in ALB.
HTTP-cookie-based stickiness that can be enabled at the target-group level.
Classic Load Balancer does not support WebSocket at all, and while a Network Load Balancer can carry WebSocket traffic over TCP/TLS listeners, it only offers source-IP affinity (and none for TLS listeners), not application-cookie stickiness. Route 53 is a DNS service and does not provide session stickiness.
Therefore, an Application Load Balancer best satisfies both the WebSocket and sticky-session requirements.
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