I managed to build a reasonably scalable product with the Java based tooling from the Jena project , along with the Python bindings - also the Clark and Parsia

I managed to build a reasonably scalable product with the Java based tooling from the Jena project , along with the Python bindings - also the Clark and Parsia tools like Stardog are quite workable. My experience is that much (SPARQL, basic reasoning) is production ready and has been for a long time, the problem is that it is hard to constrain yourself to the subset of features that don't lead to exponential computations.