AWS S3 deleteObject not working using Node JS

Question

I have implemented the AWS S3 SDK using Node.js in order to use signed URLs to upload image files to S3. This functionality is working fine but I now need a function that will delete the uploaded object. I have created the below code but it isn't working. In fact it seems that the s3.deleteObject Isn't being called at all although the function is running. I am new to Node so have probably made a silly mistake. Can somebody please help?

Setup template:

AWSTemplateFormatVersion: 2010-09-09 Transform: AWS::Serverless-2016-10-31 Description: S3 Uploader - sample application

Resources:
  # HTTP API
  MyApi:
    Type: AWS::Serverless::HttpApi
    Properties:
      # CORS configuration - this is open for development only and should be restricted in prod.
      # See https://docs.aws.amazon.com/serverless-application-model/latest/developerguide/sam-property-httpapi-httpapicorsconfiguration.html   
      CorsConfiguration:
        AllowMethods:
          - GET
          - POST
          - DELETE
          - OPTIONS
        AllowHeaders:
          - "*"   
        AllowOrigins: 
          - "*"      

  ## Lambda functions
  UploadRequestFunction:
    # More info about Function Resource: https://github.com/awslabs/serverless-application-model/blob/master/versions/2016-10-31.md#awsserverlessfunction
    Type: AWS::Serverless::Function 
    Properties:
      CodeUri: getSignedURL/
      Handler: app.handler
      Runtime: nodejs12.x
      Timeout: 3
      MemorySize: 128
      Environment:
        Variables:
          UploadBucket: !Ref MyAppS3  
      Policies:
        - S3WritePolicy:
            BucketName: !Ref MyAppS3
        ## This permission allows the Lambda function to request signed URLs
        ## for objects that will be publicly readable. Uncomment if you want this ACL.
        - Statement:
          - Effect: Allow
            Resource: !Sub 'arn:aws:s3:::${MyAppS3}/'
            Action:
              - s3:putObjectAcl
      Events:
        UploadAssetAPI:
          Type: HttpApi
          Properties:
            Path: /uploads
            Method: get
            ApiId: !Ref MyApi  

  DeleteRequestFunction:
    # More info about Function Resource: https://github.com/awslabs/serverless-application-model/blob/master/versions/2016-10-31.md#awsserverlessfunction
    Type: AWS::Serverless::Function 
    Properties:
      CodeUri: deleteObj/
      Handler: app.handler
      Runtime: nodejs12.x
      Timeout: 3
      MemorySize: 128
      Environment:
        Variables:
          DeleteBucket: !Ref MyAppS3  
      Policies:
        - S3WritePolicy:
            BucketName: !Ref MyAppS3
        - Statement:
          - Effect: Allow
            Resource: !Sub 'arn:aws:s3:::${MyAppS3}/'
            Action:
              - s3:putObjectAcl
      Events:
        deleteAssetAPI:
          Type: HttpApi
          Properties:
            Path: /delete
            Method: get
            ApiId: !Ref MyApi  

  ## S3 bucket
  SMyAppS3:
    Type: AWS::S3::Bucket
    Properties:
      CorsConfiguration:
        CorsRules:
        - AllowedHeaders:
            - "*"
          AllowedMethods:
            - GET
            - PUT
            - HEAD
          AllowedOrigins:
            - "*"

## Take a note of the outputs for deploying the workflow templates in this sample application
Outputs:
  APIendpoint:
    Description: "HTTP API endpoint URL"
    Value: !Sub "https://${MyApi}.execute-api.${AWS::Region}.amazonaws.com"
  S3UploadBucketName:
    Description: "S3 bucket for application uploads"
    Value: !Ref 'MyAppS3'    

Delete Object

/* Deletes objects from the MyApp S3 bucket */

'use strict'

const AWS = require('aws-sdk')
AWS.config.update({ region: process.env.AWS_REGION })
const s3 = new AWS.S3()

// Main Lambda entry point
exports.handler = async (event) => {
  return await deleteObj(event)
}

const deleteObj = async function(event) {
  const params = {
    Bucket: process.env.DeleteBucket, 
    Key: '66910301611586034.jpg'
  };

  s3.deleteObject(params, function(err, data) {
    if (err) {
      console.log(err, err.stack);
    } else {
      console.log('file successfully deleted');
    } 
  });
}

Get Signed Object

'use strict'

const AWS = require('aws-sdk')
AWS.config.update({ region: process.env.AWS_REGION })
const s3 = new AWS.S3()

// Change this value to adjust the signed URL's expiration
const URL_EXPIRATION_SECONDS = 300

// Main Lambda entry point
exports.handler = async (event) => {
  return await getUploadURL(event)
}

const getUploadURL = async function(event) {
  const randomID = parseInt(Math.random() * 10000000)
  const secondsSinceEpoch = Math.round(Date.now() / 1000)
  const Key = `${randomID}${secondsSinceEpoch}.jpg`

  // Get signed URL from S3
  const s3Params = {
    Bucket: process.env.UploadBucket,
    Key,
    Expires: URL_EXPIRATION_SECONDS,
    ContentType: 'image/jpeg',
    // This ACL makes the uploaded object publicly readable. You must also uncomment
    // the extra permission for the Lambda function in the SAM template.
    ACL: 'public-read'
  }

  console.log('Params: ', s3Params)
  const uploadURL = await s3.getSignedUrlPromise('putObject', s3Params)

  return JSON.stringify({
    uploadURL: uploadURL,
    Key
  })
}