If you try to execute a DynamoDB query against a Global Secondary Index, by default you’ll get this error:
AmazonDynamoDBException: Consistent reads are not supported on global secondary indexes (Service: AmazonDynamoDBv2; Status Code: 400; Error Code: ValidationException
To avoid this, per answers on this question, you need to call:
on your query expression.
Although the docs here suggest queries are eventually consistent by default, apparently with the DynamoDB mapping api you still need to explicitly set the consisten read = false parameter.