WHY A IS False? |
CONCEPT: Amazon Simple Notification Service (SNS) |
Amazon Simple Notification Service (SNS) is used for sending notifications using topics. Amazon SQS is a better solution for this scenario as it provides a decoupling mechanism where the actual images can be stored for processing. SNS does not provide anything for the images to be stored.
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WHY B IS True? |
CONCEPT: Amazon SQS |
We use Amazon SQS to decouple the front end from the processing compute layer. To do this we can create a custom CloudWatch metric that measures the number of messages in the queue and then configure the ASG to scale using a target tracking policy that tracks a certain value. |
WHY C IS False? |
CONCEPT: Target tracking policy |
- Target tracking scaling policy adds or removes capacity as required to keep the metric at, or close to, the specified target value. In addition to keeping the metric close to the target value, a target tracking scaling policy also adjusts to changes in the metric due to a changing load pattern.
- However, Using a target tracking policy with the ASG that tracks CPU utilization does not allow scaling based on the number of images being uploaded.
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WHY D IS False? |
CONCEPT: Scheduled scaling |
- Scheduled scaling helps you to set up your own scaling schedule according to predictable load changes.
- Example: - Let's say that every week the traffic to your web application starts to increase on Wednesday, remains high on Thursday, and starts to decrease on Friday. You can configure a schedule for Amazon EC2 Auto Scaling to increase capacity on Wednesday and decrease capacity on Friday.
- Using a scheduled policy is less useful as though you may be able to predict usage patterns, it would be better to adjust dynamically based on actual usage.
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Short Trick |
- Decoupled - indicates towards SQS as it is best solution to decouple the front end from the processing compute layer.
BEWARE:-
- ASG needs to dynamically adjust based on the number of images being uploaded - Indicates towards target tracking policies, which might divert you towards option C , but the earlier requirment of decoupling is not taken care in oprion C, so option C is not correct.
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References: |
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DOCS
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