When a "HTTP 400 ValidationException" error is returned due to a too large item, DynamoDB gives this message: "Item size has exceeded the maximum allowed size of 65536".
However, dynamodb-mock gives this: "Items must be smaller than 65536 bytes. Got 70116".
It is important that the text is exactly the same, because the only way to distinguish oversize errors from other validation errors is to check the error message.
P.S. Thanks for a great library!