AWS SDK 2.0 Ruby Presigned URL & transcoding the content after upload

My intention:

1. Get the presigned URL for posting a resource
2. Post resource to S3 bucket
3. Transcode my resource on s3 (for video files)

I have figured out 1 & 2 from here after hitting the route, say /getPresignedURL. Has anyone done 3?

My backup plan is to create another route, say /fileUpload which upon successful upload to the presignedURL will return a 200. I will then run a job for transcoding the video, manually. Any easier way to do this? TIA.