A company needs a graph database service that is scalable and highly available.

 The AWS service that meets the requirements of providing a graph database service that is scalable and highly available is Amazon Neptune. Amazon Neptune is a fast, reliable, and fully managed graph database service that supports property graph and RDF graph models. Amazon Neptune is designed to store billions of relationships and query the graph with milliseconds latency. Amazon Neptune also offers high availability and durability by replicating six copies of the data across three Availability Zones and continuously backing up the data to Amazon S35. Amazon Aurora, Amazon Redshift, and Amazon DynamoDB are other AWS services that provide relational or non-relational database solutions, but they do not support graph database models.