Amazon Neptune AWS graph database service

Amazon introduces an AWS graph database service called Amazon Neptune | TechCrunch

"Amazon Neptune has been specifically designed for relationship graphs. So if you’re thinking about building a social network feature, Neptune can help you.
... The database service supports graph models Property Graph and W3C’s RDF and their query languages Apache TinkerPop Gremlin and SPARQL."

Amazon Neptune - Fast, Reliable Graph Database built for the cloud

Amazon Neptune – A Fully Managed Graph Database Service | AWS News Blog

To connect to the gremlin endpoint you can use the endpoint with "gremlin" to do something like: 

curl -X POST -d '{"gremlin":"g.V()"}' https://your-neptune-endpoint:8182/gremlin

You can similarly connect to the SPARQL endpoint with "sparql"

curl -G https://your-neptune-endpoint:8182/sparql --data-urlencode 'query=select ?s ?p ?o where {?s ?p ?o}'

Amazon Neptune is in a way AWS "answer" to Microsoft Azure Cosmos DB.

Azure Cosmos DB – Globally Distributed Database Service | Microsoft Azure

But while Cosmos DB is also a globally distributed database,
AWS added similar functionality in their relational database only.

AWS adds Global Tables feature to share data across multiple geographies | TechCrunch.

"Customers using AWS’ Amazon DynamoDB to store data have two new services to help make their applications work better and more quickly in more regions around the world."

Based on features, Neptune is more a cloud-based graph database, like Neo4j:

The Neo4j Graph Platform – The #1 Platform for Connected Data

Hosting Neo4j in the Cloud - Neo4j Graph Database