<p>I am trying to understand how StackExchange recommends questions to the users.</p>

<p>Untill now, my observation is <em>tags</em> of  recommended questions are associated with <em>tags</em> user is related to (tags of questions / answers he posted and likes). However, what might be the underlying <strong>algorithm</strong> of question recommendation in StackExchange? </p>

<p>What might be an appropriate algorithm(collaborative filtering or content-based filtering) for a general question recommendation problem?</p>

<p>PS:
The recommended question list refers to:</p>

<p><img src="https://i.stack.imgur.com/XokHx.png" alt="enter image description here"></p>
