Surely S3 is a pebble compared to Dropbox?
Edit: in 2016 Dropbox stored 400PB (https://dropbox.tech/infrastructure/magic-pocket-infrastruct...), in 2018 S3 was storing multiple exabytes (https://www.quora.com/How-big-is-Amazon-S3-across-all-region...)
I suspect multiple exabytes is a low ball.
Probably -- came back to my comment 24 hours later and realized I mixed up DB and S3 in the sentence.