TimescaleDB - TimescaleDB is a time-series SQL database providing fast analytics, scalability, with automated data management on a proven storage engine.
Raygun - Raygun gives developers meaningful insights into problems affecting their applications. Discover issues - Understand the problem - Fix things faster.
KairosDB - Fast Time Series Database on Cassandra
Kafka - Apache Kafka is publish-subscribe messaging rethought as a distributed commit log.
VictoriaMetrics - Cost-effective database for huge amounts of time series data
Snare - Snare is well known historically as a leader in the event log space.