Neptune is AWS’s offering for graph databases. Now what is a graph database? It tracks the relationship between data entities, even multiple relationships between them. A great example of a graph DB would be a social network. Knowledge articles that reference each other would be another example. When you hear graph DB think AWS Neptune. Neptune can store billions of these relations and has millisecond latency as well making it a very promising offer for your graph DB, it is highly available as well with 3 AZ and up to 15 read replicas.
Amazon Keyspaces are AWS’s offering for Apache Cassandra. It is compatible with your existing Cassandra DB and utilizes the Cassandra Query Language. Amazon Keyspaces is HA and offers on-demand and provisioned capacity modes. You have low latency as well as point in time recovery for the last 35 days. Amazon keyspaces is most commonly used for IoT devices, it is very useful if you require applications with very low latency.