Redis is an open-source, networked, in-memory, key-value data store with optional durability. It is written in ANSI C. The development of Redis is sponsored by VMware.

Apache Cassandra is an open source distributed database management system. It is an Apache Software Foundation top-level project designed to handle very large amounts of data spread out across many commodity servers while providing a highly available service with no single point of failure. wikipedia.org

The Spring Framework is an open source application framework and Inversion of Control container for the Java platform. wikipedia.org

Java is a programming language and a core component of Oracle Corporation's Java Platform. The language derives much of its syntax from C and C++ but has a simpler object model and fewer low-level facilities. wikipedia.org

Apache Kafka is an open-source message broker project developed by the Apache Software Foundation written in Scala. The project aims to provide a unified, high-throughput, low-latency platform for handling real-time data feeds. wikipedia.org

Solr is an open source enterprise search platform from the Apache Lucene project. Its major features include powerful full-text search, hit highlighting, faceted search, dynamic clustering, database integration, and rich document (e.g., Word, PDF) handling. wikipedia.org

A NoSQL database provides a mechanism for storage and retrieval of data that is modeled in means other than the tabular relations used in relational databases

A Web service is a method of communication between two electronic devices over a network. wikipedia.org