Solution

Memcached

It is a high-performance, user-friendly in-memory data store. It provides a mature, scalable, open-source solution for sub-millisecond response speeds, which makes it suitable as a cache or session store. Memcached is widely used to power real-time Web, Mobile Apps, Gaming, AdTech, and E-Commerce systems.

Couch DB

The prominent big data analytics tools that use non-relational databases are MongoDB, Cassandra, Oracle No-SQL, and Apache CouchDB.
CouchDB is a NoSQL database for document storage. It provides the ability to store documents with unique names, as well as an API is known as RESTful HTTP API for reading and modifying (adding, editing, and deleting) database documents. Documents are the fundamental unit of data in CouchDB, and they also contain metadata.

Infinite graph

InfiniteGraph is a distributed graph database developed in Java and C++. It belongs to a class of "Not Only SQL" (NOSQL) database systems that emphasize graph data structures. InfiniteGraph is used by developers to discover useful and frequently hidden relationships in highly connected, complex big data sets.

Hence, option 2) is the most appropriate answer.