To create an ArcGIS Knowledge Server site, you install ArcGIS Server and authorize it with an ArcGIS Knowledge license. Therefore, the system requirements to run ArcGIS Knowledge Server are the same as the system requirements for ArcGIS Server.
The ArcGIS Enterprise deployment with which you federate the ArcGIS Knowledge Server site must have an ArcGIS Data Store graph store. See the following for information about configuring the graph store:
The only additional requirement for ArcGIS Knowledge Server is that the site must be able to communicate with the graph store. See Ports used by ArcGIS Data Store and the port diagram available from ArcGIS Enterprise system requirements for more information.
You can optionally register a NoSQL data store with your ArcGIS Knowledge Server site if you want to create a knowledge graph whose entities and relationships are stored in a NoSQL database instead of being stored in the ArcGIS Data Store graph store. Each knowledge graph must connect to its own empty NoSQL database. You will have to register one NoSQL database with the ArcGIS Knowledge Server site for each knowledge graph you create.
Neo4j is the only currently supported NoSQL database. The minimum supported version of Neo4j is 4.4.3. Neo4j Enterprise Edition is recommended. You can use Neo4j Community Edition, but you will only be able to create and use one knowledge graph at a time because of the limitations associated with this edition.
Even if you use NoSQL databases to store the entities and relationships, the ArcGIS Enterprise deployment must still include an ArcGIS Data Store graph store. The graph store contains the data model and all spatial data associated with the knowledge graph.