What is the total size of data that can be read per second using the above read throughput capacity?
Question
Your team is planning on creating a DynamoDB table and use it with their application.
They are planning to place the initial Read Capacity Unit (RCU) to 10 with the eventual read consistency.
You want to read 10 items from the table per second where each item is of size 2 KB.What is the total size of data that can be read per second using the above read throughput capacity?
Answers
Explanations
Click on the arrows to vote for the correct answer
A. B. C. D.Answer: D.
One read capacity unit represents one strongly consistent read per second,
or two eventually consistent reads per second, for an item up to 4 KB in size.
As per the question, for each 2 KB we need 1 RCU.
(means 2kb/4kb=1 RCU - rounded to the larger whole number)
So, for 10 RCU we can have up to 20KB per sec.
For eventually consistent read we need to multiply the number of items by '2', So the size of the item would be 40kB.Below is an example from AWS documentation:
Suppose that you create a provisioned table with 6 read capacity units.
With these settings, your application could do the following:
Perform strongly consistent reads of up to 24 KB per second (4 KB × 6 read capacity units).
Perform eventually consistent reads of up to 48 KB per second (twice as much read throughput).
References:
https://docs.aws.amazon.com/amazondynamodb/latest/developerguide/HowItWorks.ReadWriteCapacityMode.html https://docs.aws.amazon.com/amazondynamodb/latest/developerguide/ProvisionedThroughput.htmlTo calculate the total size of data that can be read per second, we need to consider the read capacity unit (RCU) and the size of each item.
A read capacity unit (RCU) is defined as the maximum number of strongly consistent reads per second, or the maximum number of eventually consistent reads per second, of an item up to 4 KB in size. So, if an item is larger than 4 KB, more than one RCU will be required to read it.
In this case, the table has an initial Read Capacity Unit (RCU) of 10 with eventual consistency, which means we can read 10 items of 4 KB per second. However, each item in this case is only 2 KB, so we can read twice as many items per second.
Therefore, the total size of data that can be read per second is:
10 RCU x 2 KB per item = 20 KB per second
Hence, the correct answer is option A.
