Notes on Multi-Region Consistency Global DynamoDB

AWS announced the preview of Global DynamoDB Multi-Region Strong Consistency .Eventual Consistency is the default - but a new option is available to use case requiring mult-region active\active transaction processing.

At this point the Strong Consistency is not in GA , but it is available in the following regions as a Preview

US East (N. Virginia) – us-east-1

US East (Ohio) – us-east-2

US West (Oregon) – us-west-2

Setting up is straightforward

--Create a new on-demand, single-Region table named mrscTest in the us-east-2 Region.

aws dynamodb create-table --table-name mrscTest --attribute-definitions AttributeName=TestAtt1,AttributeType=S AttributeName=TestAtt2,AttributeType=S --key-schema AttributeName=TestAtt1,KeyType=HASH AttributeName=TestAtt2,KeyType=RANGE --billing-mode PAY_PER_REQUEST --region us-east-1

aws dynamodb describe-table --table-name mrscTest --region us-east-1

--Add two new replica tables to the single-Region table in the remaining supported Regions for preview by specifying the multi-region-consistency parameter to STRONG.

aws dynamodb update-table --table-name mrscTest --replica-updates "[{\"Create\": {\"RegionName\": \"us-west-2\"}}, {\"Create\": {\"RegionName\": \"us-east-2\"}}]" --multi-region-consistency STRONG --region us-east-1

--If you only request one replica you'll get this error. 3 replicas are required
An error occurred (ValidationException) when calling the UpdateTable operation: Unsupported table replica count for global tables with MultiRegionConsistency set to STRONG.

One of the behavioural differences from Multi-Region Eventual Consistency tables is "You must create an MRSC global table by adding two replica tables to an existing single-Region table that doesn't contain any data". So how does this work for Restoring? It doesn't work .

If you restore a GlobalDynamoDB with data and then attempt to add the 2 replicas necessary to restore back to the Global DynamoDB MRSC state

aws dynamodb update-table --table-name mrscTest-restore --multi-region-consistency STRONG --replica-updates "[{\"Create\": {\"RegionName\": \"us-west-2\"}},{\"Create\": {\"RegionName\": \"us-east-2\"}}]" --region us-east-1

An error occurred (ValidationException) when calling the UpdateTable operation: Regional table cannot contain data when creating a global table with MultiRegionConsistency set to STRONG.

As mentioned in the following official document, you need to make sure that the table is an existing single-Region table and it doesn't contain any data.
----------------
https://docs.aws.amazon.com/amazondynamodb/latest/developerguide/multi-region-strong-consistency-gt.html#mrsc-preview-considerations
----------------