Redis - Redis is an open source in-memory data structure project implementing a distributed, in-memory key-value database with optional durability.
DBeaver - DBeaver - Universal Database Manager and SQL Client.
memcached - High-performance, distributed memory object caching system
DataGrip - Tool for SQL and databases
MongoDB - MongoDB (from "humongous") is a scalable, high-performance NoSQL database.
HeidiSQL - HeidiSQL is a powerful and easy client for MySQL, MariaDB, Microsoft SQL Server and PostgreSQL. Open source and entirely free to use.