An existing serverless application processes uploaded image files. The process currently uses a single Lambda function that takes an image file, performs the processing, and stores the file in Amazon S3. Users of the application now require thumbnail generation of the images. Users want to avoid any impact to the time it takes to perform the image uploads.

Change the existing Lambda function handling the uploads to create thumbnails at the time of upload. Have the function store both the image and thumbnail in Amazon S3. 

Create a second Lambda function that handles thumbnail generation and storage. Change the existing Lambda function to invoke it asynchronously. 

Create an S3 event notification with a Lambda function destination. Create a new Lambda function to generate and store thumbnails. 

Create an S3 event notification to an SQS Queue. Create a scheduled Lambda function that processes the queue, and generates and stores thumbnails.