Project Hermes is an open source key-value datastore written in Java. It has surpassed alternatives like Redis on certain benchmarks and is still in development.
To use Project Hermes all you need to do is run the jar that can be found in the releases. Project Hermes is written in Java so it is not platform-dependent and can run on any operating system.
All you need is java, then you run the jar file with a command like the one below
java -jar <jarfilename>.jar