Titan is a scalable graph database optimised for storing and querying graphs containing hundreds of billions of vertices and edges distributed across a multi-machine cluster.
Fitting huge amounts of connected data into a database not optimised for that purpose is a real challenge. Traditional relational databases do not perform well when an application needs to find out information about highly connected data (“friends of my friends” type queries). Graph databases are designed to work efficiently with highly connected data. For this reason we prefer to use graph databases when we need to do exploratory analysis on the application data.
Compared to NoSQL stores or relational databases, graph databases offer much faster access to complex connected data. If your product needs to work with large amounts of connected data items and you mainly need to answer questions that deal with the relationships between the objects, a graph database might be a good fit.