Amazon Neptune now supports SPARQL 1.1 Federated Query, a World Wide Web Consortium (W3C) Recommendation. Using Neptune customers can execute a portion of their query across different SPARQL endpoints within their Virtual Private Cloud (VPC), combine the result, and return to the user. Now customers can distribute their data across multiple Neptune clusters and using a single query to access that data across those clusters. Customers can also use federation to combine data in Neptune with data from external SPARQL endpoints.
from Recent Announcements https://aws.amazon.com/about-aws/whats-new/2019/10/amazon-neptune-now-supports-SPARQL-11-federated-query/