Is there some way to compress videos after upload on S3 ?

I double checked with our Object Storage team, and a native after-the-fact compression feature doesn't exist at this point in time.

I haven't tried it firsthand, but you could look into an s3 tool like Lambda to see how it functions with our Object Storage service. Most likely your best bet will be to either compress your videos ahead of time or download them, compress, and then re-upload (from my understanding, this is essentially what Lambda does anyway).

I found some conversations about similar situations on Stack Overflow:

• Compress file on S3
• Streaming compression to S3 bucket with a custom directory structure

The TLDR for these^^ is that a default tool doesn't quite exist yet, and the workaround solutions generally revolved around downloading, compressing, and re-uploading in one way or another.