Every Lambda function I have written that touches S3 has the same three lines of plumbing:

s3 . download_file ( bucket , key , " /tmp/input.csv " ) process ( " /tmp/input.csv " , " /tmp/output.csv " ) s3 . upload_file ( " /tmp/output.csv " , bucket , output_key )

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Download. Process. Upload. Clean up /tmp . Handle the edge case where /tmp is full from a previous invocation. Handle the edge case where the download fails halfway. Handle the edge case where you run out of the 10 GB ephemeral limit because someone uploaded a file larger than you expected.

S3 Files makes all of that go away. You mount the bucket at /mnt/workspace and use open() . The file is right there. You write the output.…