[I/O] DynamoDB / AWS Lambda: CrateDB raises `DuplicateKeyException` after Lambda is resuming CDC operations

## About
> We are observing a problem with the sync lambda.

## Problem
> Every once in a while a task will time out, which leads to the sync lambda retrying. Now, these retries fail, because, even though the original task had timed out, the data has been correctly stored into CrateDB, for all the items that are part of the batch that has timed out. Do you have any idea what could be causing this behavior?

/cc @dfeokti