[jandrewrogers]

This generalizes to most (all?) databases. Selective deletion is largely an unsolved problem at scale in databases to the extent it doesn't release the deleted resources. Under the hood databases try to turn this into selective resource truncation, which scales much better, but in most cases that is not possible without careful design of your data model.

Similarly, you often have to remind devs that in many databases an UPDATE is just an INSERT + DELETE, with all of the scaling issues implied.

[mike_hearn]

RocksDB and other LSM tree backed databases do have cheap deletes and updates, although you could argue that's because they make everything else expensive. If you have spare cores it can be a good trade though.