MongoDB - MongoDB (from "humongous") is a scalable, high-performance, open source NoSQL database.
InfluxData - Scalable datastore for metrics, events, and real-time analytics.
PostgreSQL - PostgreSQL is a powerful, open source object-relational database system.
TimescaleDB - TimescaleDB is a time-series SQL database providing fast analytics, scalability, with automated data management on a proven storage engine.
RRDTool - High performance data logging and graphing system for time series data
Prometheus - An open-source systems monitoring and alerting toolkit.