How to join tables in AWS DynamoDB?
I know the whole design should be based on natural aggregates (documents), however I'm thinking to implement a separate table for localisations (lang, key, text) and then use keys in other tables. However, I was unable to find any example on doing this.
Any pointers might be helpful!
Answer
You are correct, DynamoDB is not designed as a relational database and does not support join operations. You can think about DynamoDB as just being a set of key-value pairs.
You can have the same keys across multiple tables (e.g. document_IDs), but DynamoDB doesn't automatically sync them or have any foreign-key features. The document_IDs in one table, while named the same, are technically a different set than the ones in a different table. It's up to your application software to make sure that those keys are synced.
DynamoDB is a different way of thinking about databases and you might want to consider using a managed relational database such as Amazon Aurora: https://aws.amazon.com/rds/aurora/
One thing to note, Amazon EMR does allow DynamoDB tables to be joined, but I'm not sure that's what you're looking for: http://docs.aws.amazon.com/ElasticMapReduce/latest/DeveloperGuide/EMRforDynamoDB.html