Questions 28 to 30

Explanations for questions 28 to 30

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Question 28

An Auto Scaling group is unable to respond quickly enough to load changes resulting in lost messages from another application tier. The messages are typically around 128 KB in size.

What is the best design option to prevent the messages from being lost?

  1. Store the messages on Amazon S3.
  2. Launch an Elastic Load Balancer.
  3. Store the messages on an SQS queue.
  4. Use larger EC2 instance sizes.

Correct Answer: 3

Explanation: In this circumstance, the ASG cannot launch EC2 instances fast enough. You need to be able to store the messages somewhere so they don’t get lost whilst the EC2 instances are launched. This is a classic use case for decoupling, and SQS is designed for exactly this purpose.

Amazon Simple Queue Service (Amazon SQS) is a web service that gives you access to message queues that store messages waiting to be processed. SQS offers a reliable, highly-scalable, hosted queue for storing messages in transit between computers. An SQS queue can be used to create distributed/decoupled applications.

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