10 Things You May Not Know About Memcached

Memcached is an incredible technology that speeds up dynamic web sites and saves you time and money in the process. It’s already widely accepted as the go-to Web 2.0 distributing caching protocol and is quickly becoming a fundamental component of the dynamic web stack.

Here’s a list of the top 10 things you should know about Memcached:

1. Memcached was originally developed at LiveJournal. The site was already doing 20 million+ dynamic page views per day for 1 million users. Memcached dropped the database load by over 80%, yielding faster page load times for users, better resource utilization, and faster access to the databases.

2. Memcached represents a large chunk of the infrastructure that is used to power the most popular social networking services – Twitter, Facebook, Digg, Wikipedia, YouTube. Database-driven websites increasingly depend on distributed caching to deliver adequate performance, since scalability and reduced latency are of the utmost importance. In fact 17 of the 20 most visited sites (according to ComScore) rely on Memcached to speed up their websites. That’s every top 20 web site NOT owned by Microsoft.

3. Many of these sites have dedicated teams focused specifically on managing their Memcached deployments. Facebook alone dedicates nearly one thousand servers in their data center to Memcached (last official number: more than 800 servers supplying over 28 terabytes of memory).

4. Memcached is designed to make websites more scalable but Memcached itself is NOT easily scalable – meaning, you have may have to do your own coding to make it so.

5. RDBMSes store many types of data in two-dimensional tables that can be interrelated. However, Memcached stores everything in a single key-value table, with rare restrictions on type.

6. You can run multiple Memcached servers (e.g. instances) on one machine or on multiple machines on a network.

7. Memcached is distributed but NOT clustered. In other words, one Memcached instance knows nothing about another Memcached instance even if they are used for the same application.

8. Memcached has client libraries in all major languages including C, Java, Perl, PHP, and Python. Check out the complete list of clients here: http://code.google.com/p/memcached/wiki/Clients

9. Memcached is not persistent, has no high availability features and lacks authentication and security features.

10. Memcached can utilize existing network infrastructure. You don’t need to put in a dedicated network for Memcached traffic.