Bleemeo has published several components of the Bleemeo Cloud based Monitoring product as Open Source projects. The two main projects are Glouton, our agent based on Prometheus and Telegraf and SquirrelDB our Time Series Database based on Cassandra.
SquirrelDB, Open Source TSDB
Time Series Database with Prometheus Long Term Storage
Support pre-aggregated data for faster read
Rely on Cassandra, well known and reliable NoSQL database
Support out of the box single node and clusters architecture