This looks more like a Mongoose than like a Firebase/Firestore clone :/ You need a MongoDB instance somewhere, so this is not really a database library, it's more like query (ORM?) thing. Looks interesting nevertheless.
While not free, Firebase and Firestore have a really generous free plan quota, but big downside, in my opinion, is unnecessary complexity around setting up and working with them.
Also, there is no cloud 😛 it's just a server somewhere.
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