SAA-C03 Question 343
Single answerA company is hosting a web application on Amazon EC2 instances behind an Application Load Balancer (ALB). The application stores session data on the instances' local file system. During scaling events, users are experiencing issues with session persistence, as new instances do not have access to prior session data. What is the most cost-effective solution to ensure session persistence across scaling events?
- A
Enable sticky sessions (session affinity) on the Application Load Balancer.
- B
Store session data in Amazon DynamoDB and configure the application to retrieve session data from it.
- C
Use Amazon ElastiCache with Redis to store session data.
- D
Migrate the application to AWS Lambda and use Amazon S3 to store session data.
Show answer and explanation
Correct answer: C
Explanation
Amazon ElastiCache with Redis is ideal for storing ephemeral session data due to its low-latency, in-memory storage capabilities, which are both cost-effective and performant. This ensures session persistence across scaling events without introducing unnecessary complexity or higher costs associated with other solutions.
- A. Incorrect.
Enabling sticky sessions allows the ALB to route requests from the same client to the same instance. However, this approach does not solve the problem when an instance is terminated during scaling events, as session data is lost.
- B. Incorrect.
Storing session data in Amazon DynamoDB is an effective solution, but it may not be the most cost-effective option for storing ephemeral session data compared to alternative services like ElastiCache.
- C. Correct.
Using Amazon ElastiCache with Redis is a cost-effective and efficient solution for storing session data. It provides low-latency, in-memory storage suitable for ephemeral session data.
- D. Incorrect.
Migrating the application to AWS Lambda and using Amazon S3 for session data storage introduces unnecessary complexity and is not an optimal solution for session persistence in this scenario.