LEADING OPEN SOURCE KEY-VALUE STORE SOFTWARE
Riak combines a decentralized key/value store, a flexible map/reduce engine, and a friendly HTTP/JSON query interface to provide a database ideally suited for Web applications. And, without any object-relational mappers and other heavy middleware, applications built on Riak can be both simpler and more powerful.
Redis is an advanced key-value store. It is similar to memcached but the dataset is not volatile, and values can be strings, exactly like in memcached, but also lists, sets, and ordered sets. All this data types can be manipulated with atomic operations to push/pop elements, add/remove elements, perform server side union, intersection, difference between sets, and so forth. Redis supports different kind of sorting abilities.
Free & open source, high-performance, distributed memory object caching system, generic in nature, but intended for use in speeding up dynamic web applications by alleviating database load.
Memcached is an in-memory key-value store for small chunks of arbitrary data (strings, objects) from results of database calls, API calls, or page rendering.
Memcached is simple yet powerful. Its simple design promotes quick deployment, ease of development, and solves many problems facing large data caches. Its API is available for most popular languages.
OTHER OPEN SOURCE KEY-VALUE STORE SOFTWARE
Cassandra is a highly scalable, eventually consistent, distributed, structured key-value store. Cassandra brings together the distributed systems technologies from Dynamo and the data model from Google’s BigTable. Like Dynamo, Cassandra is eventually consistent. Like BigTable, Cassandra provides a ColumnFamily-based data model richer than typical key/value systems.
Voldemort is a distributed key-value storage system
– Data is automatically replicated over multiple servers.
– Data is automatically partitioned so each server contains only a subset of the total data
– Server failure is handled transparently
– Pluggable serialization is supported to allow rich keys and values including lists and tuples with named fields, as well as to integrate with common serialization frameworks like Protocol Buffers, Thrift, and Java Serialization
– Data items are versioned to maximize data integrity in failure scenarios without compromising availability of the system
– Each node is independent of other nodes with no central point of failure or coordination
– Good single node performance: you can expect 10-20k operations per second depending on the machines, the network, the disk system, and the data replication factor
– Support for pluggable data placement strategies to support things like distribution across data centers that are geographically far apart.
It is used at LinkedIn for certain high-scalability storage problems where simple functional partitioning is not sufficient. It is still a new system which has rough edges, bad error messages, and probably plenty of uncaught bugs.
Open source dynamo clone written in Erlang.
MemcacheDB is a distributed key-value storage system designed for persistent. It is NOT a cache solution, but a persistent storage engine for fast and reliable key-value based object storage and retrieval. It conforms to memcache protocol(not completed, see below), so any memcached client can have connectivity with it. MemcacheDB uses Berkeley DB as a storing backend, so lots of features including transaction and replication are supported.
Membrain is amassively multi-threaded implementation of memcached, optimized to exploit flash memory. Membrain delivers order-of-magnitude server consolidation, greatly simplifying your datacenter scale out for capacity and performance. Membrain also delivers persistence, for use as a highly-efficient NoSQL data store, and enterprise-grade synchronous replication and immediate failover.
LevelDB is a fast key-value storage library written at Google that provides an ordered mapping from string keys to string values.