What are the important features of Memcached?

Important features of Memcached includes
CAS Tokens: A CAS token is attached to an object retrieved from a cache. You can use that token to save your updated object.
Callbacks: It simplifies the code
getDelayed: It reduces the delay time of your script which is waiting for results to come back from a server
Binary protocol: You can use binary protocol instead of ASCII with the newer client
Igbinary:  Previously, a client always used to do serialization of the value with complex data, but with Memcached, you can use igbinary option