Because if you see OP's comment, they were testing their migrator on real users' devices (in what I presume is a blue green manner, without explicitly informing

Because if you see OP's comment, they were testing their migrator on real users' devices (in what I presume is a blue green manner, without explicitly informing them except in small print) before their "official launch". If their beta test didn't go well, they will have to rollback their change, consuming more writes. https://news.ycombinator.com/item?id=40044310 https://news.ycombinator.com/item?id=40044310