NoSQL is just a poor term. It lumps together a number of radically different approaches. Imagine a term like NoCar that would lump together airplanes, bicycles, boats, trains, and scooters, just because they are means of transportation which are not a car.

Things like Redis, Kafka, Consul, FoundationDB, RRDTool, git, S3, and plain files are all NoSQL databases of sorts. They all are useful in certain areas, all have very different features and guarantees, and each would be a poor substitute for each other or for an SQL database. (Likely even MongoDB can be useful in some areas, even though I have a hard time imagining that.)

I wish the whole "NoSQL" moniker would go away, replaced by a few terms that make more sense.

That said, the original article is a good one, laying out the upsides and downsides of a document database, and why it makes sense as a local, per-app database.