How to handle many to many in dynamodb?

@edmond_brakus 

To handle many-to-many relationships in DynamoDB, you can use a technique called "fan-out/fan-in" pattern. Here's how you can do it:

1. Fan-out: In this step, you will store the relationships between the entities in separate tables. For example, if you have two entities A and B with a many-to-many relationship, you can create two tables: AtoB and BtoA. In the AtoB table, you can store the relationships between entity A and entity B, and vice versa in the BtoA table.
2. Insert or update relationships: Whenever a new relationship is created between entities A and B, you can insert a new item in both AtoB and BtoA tables accordingly.
3. Query relationships: When you need to retrieve the relationships between entities, you can query both the AtoB and BtoA tables using the index key (e.g. A_id or B_id). This way, you can retrieve all the related entities for a given entity.
4. Delete relationships: When a relationship is deleted, you need to remove the corresponding items from both AtoB and BtoA tables.

By following these steps, you can effectively handle many-to-many relationships in DynamoDB using the fan-out/fan-in pattern.