title: Can memcache.cas and memcache.add miss?
body: <p><code>memcache.set</code> can fail if the server load is too high and <code>memcache.get</code> can fail if there is no data in the server. These are called <code>misses</code>. [Is this terminology confusing because in the <code>get</code> scenario, it didn't miss anything, it did everything correctly but there was no data, so the term <code>miss</code> is misleading?]</p>
  
  <p>However, would operations like <code>memcache.cas</code> and <code>memcache.add</code> also have this problem of <code>misses</code> and if so how is it defined? I believe they are fundamentally some kind of <code>set</code> operation so the <code>miss</code> could happen here as well?</p>
  
  <p>I couldn't find an an API documentation that specifies what happens during all scenarios. I am finding that using memcache clients makes it even difficult because each client has its own rules. Currently I am trying to understand at the server level.</p>