Redis - Redis is an open source in-memory data structure project implementing a distributed, in-memory key-value database with optional durability.
InfluxData - Scalable datastore for metrics, events, and real-time analytics.
memcached - High-performance, distributed memory object caching system
TimescaleDB - TimescaleDB is a time-series SQL database providing fast analytics, scalability, with automated data management on a proven storage engine.
MongoDB - MongoDB (from "humongous") is a scalable, high-performance NoSQL database.
Prometheus - An open-source systems monitoring and alerting toolkit.