Can there be any NoSQL that's Acidity compliant?

(Or perhaps is that even possible with NoSQL given it is simply a lot of loosely combined key-value pairs.)

Well, based on the Wikipedia article on NoSQL:

NoSQL is really a movement marketing a loosely defined class of non-relational data stores that break having a lengthy good reputation for relational databases and Acidity guarantees.

as well as:

The title was an effort to explain the emergence of an increasing number of non-relational, distributed data stores that frequently didn't make an effort to provide Acidity guarantees.

and

NoSQL systems frequently provide weak consistency guarantees for example eventual consistency and transactions limited to single data products, even though it's possible to impose full Acidity guarantees with the addition of a extra middleware layer.

So, the bottom line is, I'd say that certain from the primary advantages of a "NoSQL" data store is it's distinct lack of Acidity qualities. In addition, IMHO, the greater one attempts to implement and enforce Acidity qualities, the farther away from the "spirit" of the "NoSQL" data store you receive, and also the nearer to a "true" RDBMS you receive (relatively speaking, obviously).

However, all nevertheless, "NoSQL" is an extremely vague term and it is available to individual understanding, and is dependent heavily upon simply how much of the purist point of view you've. For instance, most contemporary-day RDBMS systems don't really stick to all of Edgar F. Codd's 12 rules of his relation model!

Going for a practical approach, it appears that Apache's CouchDB comes nearest to embodying both Acidity-compliance although retaining loosely-combined, non-relational "NoSQL" attitude.