Make a signed axios request from lambda to graphql endpoint

Hey Guys,

i have this scenario:

I use serverless framework and i use the serverless-appsync plugin. The primary auth is a cognito user pool. The additional auth is IAM.

My funtion in the serverless file looks like this:

  handleDBStreamArtist:
    handler: functions/streams/dynamodbArtist.handler
    environment:
      APP_SYNC_API_URL: !GetAtt GraphQlApi.GraphQLUrl
    events:
      - stream:
          type: dynamodb
          arn: !GetAtt ArtistTable.StreamArn
    iamRoleStatements:
      - Effect: Allow
        Action:
          - appsync:GraphQL
        Resource:
          - !GetAtt GraphQlApi.Arn
          - !Join [ '/', [ !GetAtt GraphQlApi.Arn, 'types', 'Mutation', 'fields', 'updateArtistSub' ] ]

And my lambda code looks like this:

import axios from "axios";
import gql from "graphql-tag";
import { print } from "graphql";
import { dynamoDBToJSObject } from "../../lib/DynamoDB/dynamoDBToJSObject.js";
import { aws4Interceptor } from "aws4-axios";

const interceptor = aws4Interceptor({
  options: {
    region: process.env.AWS_REGION,
    service: "appsync",
  },
});
axios.interceptors.request.use(interceptor);

//create mutation
const publishItem = gql`
  mutation updateArtistSub($id: ID!, $importSuccess: String!) {
    updateArtistSub(input: { id: $id, importSuccess: $importSuccess }) {
      id
      importSuccess
    }
  }
`;

//send mutation to trigger the subscription in appsync, nothing happens in database, just trigger the subscription
const executeMutation = async (id, importSuccess) => {
  console.info("Executing Mutation");
  const mutation = {
    query: print(publishItem),
    variables: {
      id: id,
      importSuccess: importSuccess,
    },
  };

  try {
    console.info("Attempting Axios");

    const config = {
      url: process.env.APP_SYNC_API_URL,
      method: "post",
      headers: {
        "content-type": "application/json",
      },

      data: JSON.stringify(mutation),
    };

    const data = await axios(config);
    console.log(data);
  } catch (error) {
    console.info("Error caught");
    console.log(error);
  }
};

export const handler = async (event, context, callback) => {
  for (let record of event.Records) {
    switch (record.eventName) {
      case "INSERT":
        break;

      case "MODIFY":
        const item = await dynamoDBToJSObject([record.dynamodb.NewImage]);
        let id = item[0].id;
        let importSuccess = item[0].importSuccess;
        await executeMutation(id, importSuccess);
        break;

      case "DELETE":
        console.log("DELETE");
        break;

      default:
        break;
    }
  }
  return { message: `Finished processing ${event.Records.length} records` };
};

But i always get a unauthorized error. Any Ideas?