That's a fair point. Some NoSQL products do provide ACID guarantees within the scope of a logical record. That's usually as far as they go, though. So for transactions that cross logical record boundaries and/or are commutative (i.e., the "sequence of things" matters), you would have to build the outer transaction scope in the app tier. It can be done, but it's the kind of heavy lifting that RDBMS products do pretty well. As always, right tool for the job.