DynamoDB Upsert - Update or Create?

Question

We use DynamoDB UpdateItem.

This acts as an "upsert" as we can learn from the documentation

Edits an existing item's attributes, or adds a new item to the table if it does not already exist. [...]

When we make a request, to determine if an item was created or an existing item was updated, we request ALL_OLD. This works great and allows us to differentiate between update and create.

As an additional requirement we also want to return ALL_NEW, but still know the type of operation that was performed.

Question: Is this possible to do in a single request or do we have to make a second (get) request?

Answer 1

By default this is not supported in DynamoDB, there is no ALL or NEW_AND_OLD_IMAGES as there is in DynamoDB streams, but you can always go DIY.

When you do the UpdateItem call, you have the UpdateExpression, which is basically the list of changes to apply to the item. Given that you told DynamoDB to return the item as it looked like before that operation, you can construct the new state locally.

Just create a copy of the ALL_OLD response and locally apply the changes from the UpdateExpression to it. That's definitely faster than two API calls at the cost of a slightly more complex implementation.