Which step is necessary to calculate read throughput for an application using DynamoDB?

To accurately calculate read throughput for an application using DynamoDB, it is essential to calculate the items per second that the application will read from the table. This step is vital because DynamoDB's read capacity units (RCUs) are driven by the number of items being read on a per second basis.

DynamoDB allows two types of read operations: eventually consistent reads and strongly consistent reads. An eventually consistent read consumes one read capacity unit for every 4 KB of data returned, while a strongly consistent read consumes one read capacity unit for every KB of data returned. Therefore, to estimate the read throughput required, you must know how many items per second your application will read and the average size of those items to estimate the total read capacity needed.

Focusing on the other factors mentioned helps in planning and optimization but does not directly facilitate the calculation of read throughput. For instance, estimating the size of the largest item supports understanding the potential maximum read capacity required but does not provide a throughput metric on its own. Determining the total number of tables or setting the maximum read capacity per region may also be useful for overall architecture or resource management but does not inform the specific read throughput calculation required for an effective application design with DynamoDB.