Database
C / CPP
Aerospike Database Server – flash-optimized, in-memory, nosql database
AlchemyDB is now Aerospike
Fast columnar store for analytics with PostgreSQL website
Free & open source, high-performance, distributed memory object caching system
Facebook's branch of the Oracle MySQL v5.6 database
MySQL fork maintained and used at Twitter https://github.com/twitter/mysql/wiki
Redis is an in-memory database that persists on disk. The data model is key-value, but many different kind of values are supported: Strings, Lists, Sets, Sorted Sets, Hashes website
An open-source distributed JSON document database with a pleasant and powerful query language. http://www.rethinkdb.com
Embedded key-value store for fast storage http://rocksdb.org
SSDB - A fast NoSQL database, an alternative to Redis http://ssdb.io
TokuDB is a high-performance, write optimized, compressing, transactional storage engine for MySQL and MariaDB
TokuMX is a high-performance, concurrent, compressing, drop-in replacement engine for MongoDB
VoltDB is a horizontally-scalable, in-memory SQL RDBMS designed for applications that have extremely high read and write throughput requirements.
Javascript
MongoDB is a document database that provides high performance, high availability, and easy scalability. Documents (objects) map nicely to programming language data types. Embedded documents and arrays reduce need for joins. Dynamic schema makes polymorphism easier. [website] (https://www.mongodb.org/)
Apache CouchDB is a database that uses JSON for documents,JavaScript for MapReduce indexes, and regular HTTP for its API [website] (http://couchdb.apache.org/)
dot-net
Go-lang
A low-level key/value database for Go.
A home-grown disk-backed key-value store.
An in-memory key:value store/cache (similar to Memcached) library for Go, suitable for single-machine applications.
An implementation of the LevelDB key/value database in the Go.
Groupcache is a caching and cache-filling library, intended as a replacement for memcached in many cases.
Scalable datastore for metrics, events, and real-time analytics
Ledisdb is a high performance NoSQL like Redis based on LevelDB.
Roshi is a large-scale CRDT set implementation for timestamped events.
Sky is an open source database used for flexible, high performance analysis of behavioral data.
Your NoSQL database powered by Golang.
JAVA
Cassandra is a partitioned row store. Rows are organized into tables with a required primary key.
Open Source, Distributed, RESTful Search Engine website
LMDB for Java, which is a very fast embedded key/value store with full ACID semantics.
MapDB provides concurrent Maps, Sets and Queues backed by disk storage or off-heap-memory. It is a fast and easy to use embedded Java database engine.http://www.mapdb.org
Neo4j is the world’s leading Graph Database.
OrientDB is an Open Source NoSQL DBMS with the features of both Document and Graph DBMSs.
An open source clone of Amazon's Dynamo. website
Distributed Graph Database http://titandb.io