[jerven]

MilleniumDB is an interesting engine, as is Qlever mentioned in other comments. I think both are good candidates at making RDF graphs one or two orders of magnitude cheaper to host as sparql endpoints.

Both seem to have arrived at the stage of transitioning from research to production code.

Very exiting for those of us providing our data in RDF and exposing Sparql.

AWs Neptune analytics is also very interesting, allowing Cypher on RDF graphs. Even the Oracle inbuilt RDF+Sparql seems to have improved greatly in 23ai.

[UltraSane]

It seems like writing Cypher to query RDF would be hard.