This is kind of reply to Larry Ellison's comments [1] about how Amazon can't run their business on their own databases.
I could go on... there are so many factors why it took Amazon a while to get off Oracle. Ellison is a heaping pile of dog shit fraudster. Before you dismiss me as being biased, look at my post history. I’m critical enough of Amazon.
I used to work on a team at Amazon that was _very_ relieved and happy to move away from Oracle and onto the AWS databases. I wasn't directly involved but I understand the migration work was monstrous. I think it's clear from Ellison's comment that Oracle considers that to be a product feature.