@karussell My idea was to setup a Routeplaner on a comparably small server instance and use Neo4j as Datastore for the Graph. Long story short: I tried it for about a week to optimizie Neo4j but it performed rather bad. I was able to read a Graph (I think Baden Würtemberg or even Germany). But doing Shortest Path Searches on the graph were incredibly slow and mostly timed out. I tried to use their internal Shortespath Algorithms, they can run a Dijkstra and A*.
I also had an issue, when creating a so called spatial-index on the data. Neo4j completely hung up several times when I tried to create it. They have project that is meant to care about that stuff.
I don’t know about the current state of that project. But it seems that the overall the goal of that project is not to be used for a routeplaner but more to be used for GIS queries.