TimescaleDB

TimescaleDB is an open-source time-series database built as a PostgreSQL extension. It is engineered for ingesting and analyzing massive volumes of time-stamped data in real-time, such as metrics, IoT sensor data, and financial tick data. It combines the familiarity and reliability of SQL with the performance and scalability needed for time-series workloads. Its continuous aggregates and data retention policies are powerful for real-time analytics.

While excellent for time-series, it's not a general-purpose real-time processing engine like Kafka, and complex joins can be less performant.