TerminusDB

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QuestDB

RedisGraph is the first free and open source queryable Property Graph database to use sparse matrices to represent the adjacency matrix in graphs and linear algebra to query the graph.

Neo4j is a commercially provided graph database management system developed by Neo4j, Inc. The graph database is fundamentally different to the relational model found in relational database management systems (RDBMS). With Neo4j, each data record, or node, stores direct pointers to all the nodes it's connected to. The database is also designed to perform complex queries with complex connections orders of magnitude faster. Neo4j is ACID-compliant and suited for projects that requires complicated relationship structures.

JanusGraph is a free and open-source distributed, scalable graph database optimized for storing and querying graphs containing hundreds of billions of vertices and edges distributed across a multi-machine cluster. The project is managed by The Linux Foundation and is released under the Apache Software License 2.0. Large corporations like Expero, Google, GRAKN.AI, Hortonworks, IBM and Amazon also supports the project.

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.