When we launched Facebook Video at the end of May, one of my favorite features was being able to record a video of myself within a message and then send it to my friends. Soon the Video team realized that we also sent friends messages in the form of Wall posts, so we started working on video attachments for the Wall too.

At the same time, we noticed other platform applications building their own walls - ways to leave various sorts of messages behind. We realized it made sense not just to add videos to Wall posts, but to make the Wall a more central place that any platform application could add content to. As a result, we have now launched an improved Wall.

So now, the Wall isn't a place where you only write to your friends - if you want to record a video on someone's Wall, you can do that. If you want to draw on their Wall or post a song to their Wall, you can do that too - as long as there's an application built for it. It's another way for developers to make applications fit into Facebook and another way for you to share your favorite applications with your friends.

Kevin, an engineer at Facebook, is recording karaoke videos on his friends' Walls.

Early this morning, Facebook hit a new milestone—we now have thirty million active members on the site. Welcome to Facebook, everyone!

We asked ourselves this question more than once while working on improvements to search in March 2006. At the time, there were bigger search engines out there, including some good open source ones, that we could have used to power Facebook search results. However, we decided that searches carried out on Facebook had a particular structure that only we could understand and optimize for. We wrote a crawler for the site, created an in-memory reverse index using both hashes and ternary tries and created a ranking system that scaled to return unique results for over 28 million user profiles.

Some quick stats about Facebook search:

• Over 600 million searches per month. This makes us one of the top 20 search engines on the web in terms of number of searches.
• Approximately 1 terabyte of in-memory data.
• Average search query time of less than 100ms.
• Most used people search engine on the web.

Facebook search results are sorted by an approximation of social graph distance. People closer to you in the graph—your friends and people in your networks—are likely to be more relevant to you and thus are ranked higher. We also use this concept of "social proximity" to order results within applications like groups and events. Facebook search's key differentiator is that search results are unique to every user because they are based on a individual's place in the social graph.

We have big plans to improve Facebook search in the upcoming months. We want to leverage the power of the social graph to further improve the quality of the results and ensure that you find what you are looking for on Facebook.



Aditya Agarwal, a Facebook Tech Lead, is searching for an answer...