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POPulling wall/dashboard data like facebook, twitter, tumblr, etc
 

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    <p>I feel this must be asked elsewhere, but I couldn't figure out the correct search words to find an answer. If this is a duplicate, please point to correct response elsewhere.</p> <p>Services like Facebook, Twitter, Tumblr, and I'm sure a whole host of others allow you to follow other users. Their posts then appear on a wall or dashboard. I'm wondering how, with such large data sets, these services can pull posts so quickly. I assume they are not using a SQL server and they are not doing something like:</p> <pre><code>SELECT * FROM `posts` WHERE `poster_id` IN ( super long list of users being followed ) ORDER BY `date` LIMIT 10; </code></pre> <p>As the above could have a very large list of user ids in it, and it likewise wouldn't work very well with sharding, which all these large services use.</p> <p>So, can anyone describe what kind of queries, algorithms, or databases these services use to display the followed posts?</p> <p>Edit: Thanks for everyone's responses. It seems like the most likely way of doing this is via a graph database such as GraphDB, Neo4j or FlockDb, the latter of which is Twitter's graph database. With Neo4j, it is done something like what is documented at <a href="http://docs.neo4j.org/chunked/milestone/cypher-cookbook-newsfeed.html" rel="nofollow">http://docs.neo4j.org/chunked/milestone/cypher-cookbook-newsfeed.html</a>.</p> <p>Of course, Google, Facebook, etc., all have their own, internally built or internally modified databases for their unique use cases.</p>
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