You need your API backed by DynamoDB to stay online during a total regional AWS failure. You can tolerate a couple of minutes of lag or slowness during a large failure event, but the system should recover with normal operation after those few minutes. What is a good approach?

Answer options:

A.Set up DynamoDB cross-region replication in a master-standby configuration, with a single standby in another region. Create an Auto Scaling Group behind an ELB in each of the two regions for your application layer in which DynamoDB is running in. Add a Route53 Latency routing using the ELBs in the two regions as the resource records.
B.Set up a DynamoDB Global table. Create an Auto Scaling Group behind an ELB in each of the two regions for your application layer in which the DynamoDB is running in. Add a Route53 Latency DNS Record with DNS Failover, using the ELBs in the two regions as the resource records.
C.Set up a DynamoDB Multi-Region table. Create a cross-region ELB pointing to a cross-region Auto Scaling Group, and direct a Route53 Latency DNS Record with DNS Failover to the cross-region ELB.D.Set up DynamoDB cross-region replication in a master-standby configuration, with a single standby in another region. Create a cross-region ELB pointing to a cross-region Auto Scaling Group, and direct a Route53 Latency DNS Record with DNS Failover to the cross-region ELB.

Answer – B
#Updated based on latest AWS updates
Option A is invalid because using Latency based routing will send traffic on the region with the standby instance. This is an active/passive replication, and you can`t write to the standby table unless there is a failover. Answer A can work only if you use a failover routing policy.
Option D is invalid because there is no concept of a cross-region ELB.Amazon DynamoDB global tables provide a fully managed solution for deploying a multi-region, multi-master database without building and maintaining your own replication solution. When you create a global table, you specify the AWS regions where you want the table to be available. DynamoDB performs all of the necessary tasks to create identical tables in these regions and propagate ongoing data changes to all of them.
For more information on DynamoDB GlobalTables, please visit the below URL:
https://docs.aws.amazon.com/amazondynamodb/latest/developerguide/GlobalTables.html