IonDB vs KairosDB: What are the differences?
IonDB: A key-value store for microcontroller and IoT applications. Currently in the Arduino world, there doesn't exist an associative array or map implementation that is both easy to use and performance competitive. There also is little support for disk based storage options that don't involve writing it yourself. IonDB is fast, functional, and offers disk based storage out of the box; KairosDB: Fast Time Series Database on Cassandra. KairosDB is a fast distributed scalable time series database written on top of Cassandra.
IonDB and KairosDB belong to "Databases" category of the tech stack.
IonDB and KairosDB are both open source tools. It seems that KairosDB with 1.46K GitHub stars and 302 forks on GitHub has more adoption than IonDB with 525 GitHub stars and 37 GitHub forks.