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.