keen-io refers to the libraries and APIs produced for event analytics by the "Keen IO" company.
Keen IO provides a modern and massively scalable analytics API including libraries for data collection, querying, and visualization.
Keen IO collects arbitrary events in JSON format, automatically ingesting any new events and rich custom properties you send. Keen IO's query APIs make it straightforward to run counts, sums, segmentation, and more.
Keen IO is typically viewed as an alternative to building and maintaining your own in-house analytics backend. It is commonly used to build custom/advanced analytics solutions, embed analytics reports into apps, and white label analytics for customers.