Memcache is one of the App Engine services. It is a volatile-memory key-value store. It operates over all your JVM instances; as long as an item remains in Memcache, it can be accessed by any of your application's processes.
Memcache contents remain indefinitely if you don't set them to expire, but can be removed ("evicted") by App Engine at any time. So, never count on a Memcache entry to exist in order for your application to work correctly. The service is meant only as a cache that allows you quicker access to information that you would otherwise obtain from the Datastore or have to generate. Memcache is often used both for storing copies of data objects and for storing relatively static display information, allowing web pages to be built more quickly.
Transactions over Memcache operations are not supported—any Memcache changes you make within a transaction are not undone if the transaction is rolled back.
The basic Memcache operations are put
, get
, and delete
: put
stores...