Instagram kept deleted photos and messages on its servers for more than a year
Whenever someone publishes an article like this, I want them to find out what its like when you reach the threshold of 100000 individual delete requests per second which ends up being five million actual deletes when you factor in all of the associated references to the item being deleted and its metadata.  Then I want them to find out what happens when you have to propagate those deletes across geographically distributed data centers, clear a geographically distribute cache and do it in a way that minimizes user facing errors and guarantees consistency.  Finally you have to also ensure that deletions don't effect any business facing applications since ad revenue and metrics are all generated from certain types of data.These people imagine you just rm -rf a file and run a few SQL queries, you literally can't just delete data.  I've worked at the scale of Instagram before.  Literally nothing works like that at that scale, the person who wrote that article should have called up someone from Instagram and had them explain at a really high level how complicated deleting data is at large scale.