Almost everyone has a Facebook account, even people who are not familiar with the Internet. With millions people actively using Facebook, updating their status, replying to messages, uploading photos and so on, how is Facebook's page still loading very fast?
I was told that Facebook was built using only PHP and MySQL, so how can Facebook's performance be so good?
Facebook uses HipHop, which converts PHP into C++ code (which is then compiled into much more efficient machine code than actual PHP).
Facebook has data distributed across many, many servers. They actually use Hadoop clusters for most of their data storage. In fact I doubt Facebook is using MySQL in any significant way at this point.
They have a compiled version of php, in fact. My guess would have to be: insane amounts of crazy hardware, brutally efficient code, and a database structure optimized with caching, denormalization, clustering...
Facebook was not only using MySql - it started out using Cassandra, and is migrating over to HBase. Applications like FB need a highly scalable Database.
Ultimate reason: http://memcached.org/
They claim 98% of everything you see on Facebook is from their massive memcache server cluster.
Check out http://facebook.com/techtalks.
They have some great videos describing many of their various optimizations. For instance, there's a talk on memcached (which helps speed up common key gets) and their front-end optimizations (doing lazy loading of Javascript, etc).
The amazing part is how large everything is at facebook. With millions of users and thousands of servers, even a seemingly small optimization can end up saving them millions of dollars or gigabytes of memory.
Because they have a lot of money. Hiring smart developers and buying tons of servers every week is quite costly.
This article talks about the inner workings of Facebook: http://royal.pingdom.com/2010/06/18/the-software-behind-facebook/
Maybe a small part of the solution overall, but they also optimize for fast client-side rendering. They contracted CSS expert Nicole Sullivan to do some optimization based on her OOCSS techniques.
Watch this presentation of Aditya Agarwal, Director of Engineering at Facebook, this presentation talks about Facebook’s architecture and its major components (LAMP (PHP, MySQL), Memcache, Thrift, Scribe).
XHP is a PHP extension which augments the syntax of the language such that XML document fragments become valid PHP expressions. - GIT checkout and Wiki
It's worth looking into how Facebook selectively loads front end JS so that there is very little latency in the responsiveness of the UI.
By
Last I heard, they had about 7000 + servers. It also helps that Zuckerberg and his employees are geniuses.
There is a lot of information about their technology in the Facebook Group Facebook Engineering, including discussions of their MySQL cluster, XHP, memcached, etc.
It comes down to having enough money to hire smart staff who write efficient programs running on many many computers.