Review Mode Practice Test 3 – Q59

[ClaireS]

Hello,

I disagree somewhat with the answer for this question. Developing an ElastiCache layer will require code/app changes and this will incur a cost which could be quite expensive when weighed up against the cost of a scale out event. I’d like to understand the rationale here to opt for ElastiCache over a scale out event?

Thanks,

Claire

[Kenneth-Samonte-Tutorials-Dojo]

Hi ClaireS,

Thank you for your feedback.

Can you share the whole question here? The questions are shuffled, so my Test 3, Q59 is different from yours.
I would like to review the question to give you a proper response.

Thank you,

Kenneth (Tutorials Dojo)

[ClaireS]

Apologies Kenneth 😃 I have been experiencing issues attached images to my posts so I don’t think it went on the first time. Hoping this works…

[Kenneth-Samonte-Tutorials-Dojo]

Hello ClaireS,

Thank you for your reply.

Yes, I agree that updating the application to support ElastiCache can incur development costs. However, there are other factors to consider here.

First, this is an AWS exam question and AWS wants to promote the proper use of its services as much as possible, and the use case for ElastiCache fits this scenario – Auto Scaling EC2 instances and RDS instances.

Furthermore, the development cost is a one-time cost for the application. After that, your ElastiCache can bring you cost savings in the long run while getting the target of 3 second response time.

Since there is a cache, the DB lookups will be faster, and the RDS instances won’t have to work as much. So since requests are fulfilled faster, the EC2 instances can serve more requests in the same time period, you can have a lower instance count on your EC2 cluster, you don’t have to upscale your RDS instances since there is a cache to fulfill frequent requests. This will save you money in the long run.

A scale-out event is ideally recommended to handle the load when there are spikes in traffic. However, you can’t reduce the response time from 7 seconds to 3 seconds if the RDS lookup on the backend database takes too long, no matter how many EC2 instances you have on your cluster.

Hope this helps.

Let us know if you need further assistance. The Tutorials Dojo team is dedicated to helping you pass your AWS exam!

Regards,

Kenneth Samonte @ Tutorials Dojo