what is wrong in this prefix comparator dynamodb stream fillter pattern?

Question

Hi, I try to filter dynamodb stream events with the following pattern:

```
"MaximumRetryAttempts": 1,
        "FilterCriteria": {
          "Filters": [
            {
              "Pattern": "{\"eventName\":[\"INSERT\",\"MODIFY\",\"REMOVE\"],\"dynamodb\":{\"NewImage\":{\"PK\":{\"S\":[{\"prefix\":[\"BOOK\"]}]}}}}"
            }
          ]
```
However, Cloudformation throws an error saying it is invalid. I can not see the error here? What am I doing wrong?

Answer

Answering my own question for someone who stumbles upon this. Apparently, for the prefix comparator, you do not need extra brackets.  The following is correct:

```
 "Filters": [
            {
              "Pattern": "{\"eventName\":[\"INSERT\",\"MODIFY\",\"REMOVE\"],\"dynamodb\":{\"NewImage\":{\"PK\":{\"S\":{\"prefix\":[\"BOOK\"]}}}}}"
            }
          ]
```

what is wrong in this prefix comparator dynamodb stream fillter pattern?

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