QuestDB

vs

Redis

TimescaleDB is a leading open-source relational database for time-series data. The database is provided as fully managed or self‑hosted software, giving the power of choice back to developers and organizations. Timescale gives you all the reliability and flexibility of PostgreSQL. It allows you to use regular SQL to construct queries to better understand your products and your users. While achieve 10-100x faster queries than PostgreSQL, InfluxDB, and MongoDB with native optimizations for time-series.

A Chinese developed open-source NewSQL database that supports analytical processing and hybrid transactional workloads. TiDB is licensed under the Apache 2.0 license and primarily developed by PingCAP, Inc. The database provides high availability with strong consistency and horizontal scaling and is compatible with MySQL.

OpenTSDB is a free and open-source distributed, scalable Time Series Database written on top of Apache HBase. OpenTSDB was designed to address a common need: store, index and serve metrics collected from computer systems such as network gear, operating systems and applications, at a large scale, and make this data easily accessible and graphable. OpenTSDB allows you to collect thousands of metrics from tens of thousands of hosts and applications, at a high rate and will never delete or downsample data and can easily store hundreds of billions of data points.

Memcached is a free and open-source in-memory key-value store used for storing small chunks of data objects in dynamic memory. Most commonly, Memcached is used to speed up dynamic database-driven websites by caching data and objects in RAM to reduce the number of times an data sources needs to be fetched. Rather than querying the database for each unique request, Memcached can be used to store data from common pages in memory and speedup and improve the experience of a web application or website.

Apache Cassandra is a free and open-source, distributed, wide column store, NoSQL database management system. Apache Cassandra is designed to handle large amounts of data across many commodity servers, providing high availability with no single point of failure. The database has become the choice of many organizations that need scalability and high availability without compromising performance. Apache Cassandra also provides support for replicating across multiple datacenters, providing lower latency for end users of Cassandra-powered applications.

MongoDB is an open-source document-oriented distributed database built for modern applications. MongoDB uses JSON-like documents with optional schemas and is classified as a NoSQL database. The database is freely distributed under the Server Side Public License, but MongoDB provides commercial version of the database for enterprise-scale applications.