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  • A client-server application over TCP or UDP
  • Free: Open source distributed under Berkeley Software Distribution (BSD) license.
  • A big hash table which is a key-value dictionary of strings, or objects, stored in memory. It's a key-value database that caches database queries or API calls or page rendering to accelerate the web applications performance.
  • Highly scalable performance oriented systems: speed up dynamic web applications by reducing the load
  • Used by most big brands which include Facebook, YouTube, Flickr, Wikipedia, Netlog, Twitter and other millions of websites

memcached - a distributed memory object caching system


  • Configure Memcached


$ yum install memcached
$ apt-get install memcached

It runs on a default port 11211

$ ps -aux | grep memcached

Telnet to connect to Memcached connection

$ telnet host port

Commands: set, add, replace, append, prepend, cas, delete, stats

Set command

  • key: the name by which data stored and retrieved
  • flags: a 32-bit unsigned integer stored with data provided by a user and returns when retrieved
  • exptime: expiry time in seconds, 0 means no delay and for more than 30 days it uses the UNIX timestamp
  • bytes: length or number of bytes in a data block stored
  • noreply: parameter to inform the server to not to send any reply
  • value: data stored

Latest News

  • (August 10, 2018) Future Hosting warns server Hosting clients to check insecure Memcached instances misconfigured for DDoS attack risk as reported by CSO online. It can be used to amplify the data in a DDoS attack by a factor of more than 50,000. Early 2018, a DDoS attack that peaked at 1.35 TB per second recorded.