Global Tables - AWS Certification Exam Question

Answer: C.

1 local +2 replica = 10+10+10=30,30X2 = 60

Using DynamoDB auto scaling is the recommended way to manage throughput capacity settings for replica tables that use the provisioned mode.

DynamoDB auto scaling automatically adjusts read capacity units (RCUs) and write capacity units (WCUs) for each replica table based upon your actual application workload.

For more information, see Managing Throughput Capacity Automatically with DynamoDB Auto Scaling.

If you create your replica tables using the AWS Management Console, auto scaling is enabled by default for each replica table, with default auto scaling settings for managing RCUs and WCUs.

Changes to auto scaling settings for a replica table or secondary index made through the DynamoDB console or using the UpdateGlobalTableSettings call are applied to all of the replica tables and matching secondary indexes in the global table automatically.

These changes will overwrite any existing auto scaling settings.

This ensures that provisioned write capacity settings are consistent across the replica tables and secondary indexes in your global table.

If you use the UpdateTable, RegisterScalableTarget, or PutScalingPolicy calls, you should apply the change to each replica table and matching secondary index individually.

Note:

If auto scaling doesn't satisfy your application's capacity changes (unpredictable workload) or if you don't want to configure its settings (target settings for minimum, maximum, or utilization threshold), you can use on-demand mode to manage capacity for your global tables.

For more information, see On-Demand Mode.

If you enable on-demand mode on a global table, your consumption of replicated write request units (rWCUs) will be consistent with how rWCUs are provisioned.

For example, if you perform 10 writes to a local table that is replicated in two additional Regions, you will consume 60 write request units (10 + 10 + 10 = 30; 30 x 2 = 60).

https://docs.aws.amazon.com/amazondynamodb/latest/developerguide/globaltables_reqs_bestpractices.html

In this scenario, QuickDialog is using DynamoDB to support their mobile application, and they have implemented a global table to replicate their data across multiple regions.

A global table in DynamoDB is a fully managed, multi-region, and multi-master database table that automatically replicates data across multiple regions, providing low latency and high availability. In this case, QuickDialog is using global tables to ensure that their users' data is replicated across multiple regions, providing better performance and availability.

When performing writes to a global table, DynamoDB calculates the write capacity unit (WCU) usage based on the number of regions where the table is replicated. In this case, the table is replicated in two additional regions, so the WCU usage will be multiplied by 3 (the original region plus the two additional regions).

Each write to a local DynamoDB table consumes one WCU, which means that if you perform 10 writes to a local table, you would consume 10 WCUs. However, because this table is replicated in two additional regions, the WCU usage will be multiplied by 3, which means that the total WCU consumption would be:

10 writes x 3 regions = 30 WCU's

Therefore, the correct answer is A. 30 WCU's.