gislenius
RumbleDB is free, with no restriction on commercial use, and open source. It is an academic project, the product of now 6 years of work by 20+ ETH Zurich BSc and MSc students in their projects and theses.
You will find a video tutorial given at the Declarative Amsterdam conference last year here: https://www.youtube.com/watch?v=3YkLXQVyN2o (link edited, it was wrong)
RumbleDB works with small JSON files but also with several terabytes of JSON. It also works with many other formats; for example, it allows validating data and then storing it in a more efficient binary format (like Parquet).
It works on a laptop by spreading the computations on all the cores, but also in the cloud (it was tested on a cluster of 64 Amazon EMR machines manipulating billions of objects).
It can read and write data to and from a laptop's local drive, but also to and from data lakes (S3, HDFS...).
Feature-wise, JSONiq can do everything SQL can do (projection, selection, grouping, sorting, joins, etc), while also supporting heterogeneous and nested datasets seamlessly (normalization, denormalization, navigation, etc). 95% of it is directly based on a W3C standard including many of its builtin functions.
RumbleDB also has a Machine Learning library.