title: What is the default expiry time for Rails cache?
body: <p>I've done some googling and couldn't find the answer to this question. Rails allows to specify expiry times for its cache like that:</p>
  
  <pre><code>Rails.cache.fetch("my_var", :expires_in =&gt; 10.seconds)
  </code></pre>
  
  <p>But what happens if I specify nothing:</p>
  
  <pre><code>Rails.cache.fetch("my_var")
  </code></pre>
  
  <p>It never expires? Is there a default value? How can I explicitly define something that never expires?</p>