Invalid Answer to Question - AWS Big Data Specialty

I have searched high and low for any signs of DynamDB spots instance and none have been found. I think the wording is confusing because reserved instances exist for DynamodDB and A is invalid because it could imply the word "both" at the beginning of the sentence. The same is true for choice C. The word "both" could be implicitly understood by someone and it would render even choice C invalid as currently written.

You are using a MapReduce job to analyze the activation of an item you sell. The job is able to tolerate interruptions and occasional instance termination. The number of activations is usually steady throughout the year, except the week before Christmas, where there is a 20X increase. You need to be sure you have both a solution that will consistently provide low-latency performance and one that will allow you to expand processing power significantly when needed to process the additional data. What is the most cost-effective and performance-optimized solution?

A. Amazon DynamoDB and Amazon Elastic MapReduce with Reserved instances

B. Amazon RDS and Amazon Elastic MapReduce with Spot instances.

Why is this incorrect?

Incorrect. RDS is a potential solution, but an overwhelming amount of traffic at a single time might reduce performance.

C. Amazon DynamoDB and Amazon Elastic MapReduce with Spot instances.

Why is this correct?

Correct. DynamoDB is a fully managed NoSQL database service that provides fast and predictable performance with seamless scalability. Spot instances allow you to bid on spare Amazon EC2 computing capacity. Since Spot Instances are often available at a discount compared to On-Demand pricing, you can significantly reduce the cost of running your applications, grow your application’s compute capacity and throughput for the same budget, and enable new types of cloud computing applications.

D. Amazon RDS and Amazon Elastic MapReduce with Reserved instances.


  • post-author-pic
    biju.krishnan-7f2dc57f
    12-17-2018

    My 2 cents on this topic
    DynamoDB does not have any "SPOT" or "RESERVED" instances as you do not scale dynamoDB in those terms. You scale by choosing the right partition key and correct values for read capacity and write capacity. There are two modes to factor in capacity
    1. On demand mode: Here you let DynamoDB bill you as per use.
    2. Provisioned mode: Here you specify the RCU and WCU values and pay predictable costs, but suffer throttling if your applications needs more performance than you planned.

    I think for the question above, where cost effectiveness and scalability are primary requirements, "C" is definitely the best choice.

  • post-author-pic
    Corey C
    12-19-2018

    DynamoDB does indeed have reserved instances. The issue is whether or not it has Spot Instances if you can construe the perhaps accidentally implied meaning of the word " both" at the beginning of each potential correct answer. 

  • post-author-pic
    andru.estes-e6154ef9
    12-20-2018

    DynamoDB does not offer reserved instances, it offers provisioned throughput where you can set the write and read capacity, but that is not the same thing as a reserved instance. The whole point of it is to be a managed, serverless NoSQL offering. Just an FYI. 

  • post-author-pic
    Broadus P
    12-20-2018

    Good Evening, please let me know which quiz this is or if its the final exam

  • post-author-pic
    Corey C
    12-23-2018

    Andru, thank you for making the point crystal clear! :)

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