title: If a GET request's response changes, is idempotency respected?
body: <p>I am reading a lot about rest API and I always stumble upon terms idempotency. Basically GET, HEAD, PUT, DELETE and OPTIONS are all idempotent, and POST is not. </p>
  
  <p>This statement on <a href="http://www.restapitutorial.com/lessons/idempotency.html" rel="noreferrer">http://www.restapitutorial.com/lessons/idempotency.html</a> made me doubt my understanding of idempotency.</p>
  
  <blockquote>
    <p>From a RESTful service standpoint, for an operation (or service call)
    to be idempotent, clients can make that same call repeatedly while
    producing the same result. In other words, making multiple identical
    requests has the same effect as making a single request. Note that
    while idempotent operations produce the same result on the server (no
    side effects), the response itself may not be the same (e.g. a
    resource's state may change between requests).</p>
  </blockquote>
  
  <p>So does idempotency actually has something to do with server-work or a response? </p>
  
  <p>What confuses me if I have</p>
  
  <pre><code>GET /users/5
  </code></pre>
  
  <p>returning</p>
  
  <pre><code>{
  "first_name" : "John",
  "last_name" : "Doe",
  "minutes_active": 10
  }
  </code></pre>
  
  <p>and then do the same request after one minute I would get</p>
  
  <pre><code>GET /users/5
  {
  "first_name" : "John",
  "last_name" : "Doe",
  "minutes_active": 11
  }
  </code></pre>
  
  <p>How is this idempotent?</p>
  
  <p>Furthermore if response contains some kind of UUID which is unique for each response, would that break idempotency?</p>
  
  <p>And finally, is idempotency same server-work over and over again, or same results over and over again for the same/single request?</p>