Yes this was completely ignored by the article. This along with a 'where' clause can guarantee the operation will only succeed iff there is sufficient funds. I don't know if other NoSQL DBs offer these sort of atomic operators.

Which makes this statement seem particularly unfair: "The problem here stemmed from the broken-by-design interface and semantics offered by MongoDB." He seems to call out Mongo by name a couple times but doesn't say that the exchange was actually using Mongo.