The current shex-simple interface runs over SPARQL and spends 99.99% of its time waiting for SPARQL. The SPARQL endpoint downgrades responsiveness to shex-simple after about 60 queries which makes any sizable validation very slow.

Remediation:

1. move shex validation to a Blaze instance and run directly over the API.
2. (less preferrable) tell SPARQL query service not to downgrade shex-simple interface.