Amazon ElastiCache is a fully managed, highly available, scalable, in-memory data store and cache and provides support for two popular open source engines, Redis and Memcached, and is protocol compliant with both. ElastiCache provides an easy migration path for those desiring a fully managed alternative to self-managed in-memory store/cache, often as easy as simply changing an application configuration setting. ElastiCache is a member of the AWS database family of services which also includes RDS, Redshift and DynamoDB.
Amazon Neptune Amazon Neptune is a fully managed graph database service with built-in support for Property Graph and Resource Description Framework (RDF) models, and SPARQL and TinkerPop Gremlin query languages. With Neptune you can easily implement solutions for popular use cases in social networking, life sciences and IT operations. Pay-for-what-you-use pricing makes the AWS managed Neptune service an attractive alternative to self managing your own database cluster. See the Neptune product page for additional information.