Lambda event filtering for DynamoDB - event_name INSERT not working

Question

I have DynamoDB set as trigger for my lambda function and the following filter criteria, which is not working.
```
{"event_name": ["INSERT"]}
```

I've gone through some examples of properly written filters, but this fails to trigger the lambda.
Furthermore, details of my lambda fn is as below.
![Enter image description here](/media/postImages/original/IM9hHJzwkZSASIC3KuiAFwyQ)
Where does "key" here come from and what does it represent in the `Event` I am passed to my handler?
Here is what my `Event` looks like;
```
Event { 
    records: [
        EventRecord { 
            change: StreamRecord { 
                approximate_creation_date_time: ___ 
                keys: {"id": String("___")}, 
                new_image: {
                   ....
                    "valid": Boolean(true), 
                }, 
               ...
            }, 
            ...
            event_name: "INSERT", 
            event_source: Some("aws:dynamodb"), 
            table_name: None 
        }
    ] 
}
```

Other things bother me like seeing `table_name` blank because the trigger is specifically being called when data is changed in an specific, existing table.

Accepted Answer

As you can [here](https://docs.aws.amazon.com/amazondynamodb/latest/developerguide/Streams.Lambda.Tutorial2.html), the event that your Lambda receives is like this:

```
{
  "eventID": "c9fbe7d0261a5163fcb6940593e41797",
  "eventName": "INSERT",
  "eventVersion": "1.1",
  "eventSource": "aws:dynamodb",
  "awsRegion": "us-east-2",
  "dynamodb": {
    "ApproximateCreationDateTime": 1664559083.0,
    "Keys": {
      "SK": { "S": "PRODUCT#CHOCOLATE#DARK#1000" },
      "PK": { "S": "COMPANY#1000" }
    },
    "NewImage": {
      "quantity": { "N": "50" },
      "company_id": { "S": "1000" },
      "fabric": { "S": "Florida Chocolates" },
      "price": { "N": "15" },
      "stores": { "N": "5" },
      "product_id": { "S": "1000" },
      "SK": { "S": "PRODUCT#CHOCOLATE#DARK#1000" },
      "PK": { "S": "COMPANY#1000" },
      "state": { "S": "FL" },
      "type": { "S": "" }
    },
    "SequenceNumber": "700000000000888747038",
    "SizeBytes": 174,
    "StreamViewType": "NEW_AND_OLD_IMAGES"
  },
  "eventSourceARN": "arn:aws:dynamodb:us-east-2:111122223333:table/chocolate-table-StreamsSampleDDBTable-LUOI6UXQY7J1/stream/2022-09-30T17:05:53.209"
}
```

As you only want inserts, your filter pattern should look like this:

```
{ "eventName": ["INSERT"]}
```

In your case you specified `event_name`.

Lambda event filtering for DynamoDB - event_name INSERT not working

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