6.1 Overview

Memcached is a distributed in-memory caching server using a simple text-based protocol, commonly used for key-value data stores, with clients available for many platforms and programming languages. The most recent release of the memcached server is available from memcached.org.

The Memcache API for NDB Cluster is implemented as a loadable storage engine for memcached version 1.6 and later, which employs a storage engine architecture. This API can be used to provide a persistent NDB Cluster data store which is accessible employing the memcache protocol. It is also possible for the memcached server to provide a strictly defined interface to existing NDB Cluster tables such that an administrator can control exactly which tables and columns are referenced by particular memcache keys and values, and which operations are allowed on these keys and values.

The standard memcached caching engine is included in the NDB Cluster distribution. Each memcache server, in addition to providing direct access to data stored in NDB Cluster, is able to cache data locally and serve (some) requests from this local cache. As with table and column mappings, cache policies are configurable based on a prefix of a memcache key.