joining two DynamoDB tables that exist in different AWS accounts directly through a query or operation like a SQL JOIN is not natively supported by DynamoDB. DynamoDB is a NoSQL database, and it does not have built-in support for traditional SQL-like joins.
However, there are alternative approaches to achieve data integration and querying across multiple DynamoDB tables in different AWS accounts:
Cross-Account IAM Role: You can set up cross-account access by creating an IAM role in the account where the tables exist and granting permissions to the other AWS account to assume that role. This way, the second AWS account can assume the role temporarily, gain access to the first account's DynamoDB tables, and perform the necessary operations. AWS Security Token Service (STS) is used for this kind of cross-account access.
Data Replication: If you need to perform frequent joins across tables in different accounts, you might consider replicating the relevant data from one account's DynamoDB table to the other account's table. This replication can be done using AWS Lambda functions or services like AWS Data Pipeline, AWS Glue, or Amazon DynamoDB Streams. By keeping the data synchronized, you can effectively query and work with data from both tables in each account.
Data Aggregation: In certain cases, instead of performing actual joins, you can design your data models and applications in a way that allows you to perform data aggregation or enrichment in one account based on data from another account. This approach involves denormalizing and pre-processing data before storing it in DynamoDB to minimize the need for joins.
Remember that data access and security should be appropriately managed when working with data across multiple AWS accounts. The cross-account IAM role approach allows you to control access and permissions effectively, ensuring data privacy and security.