title: Understanding Kafka Topics and Partitions
body: <p>I am starting to learn Kafka, during my readings, some questions came to my mind:</p>
  <ol>
  <li><p>When a producer is producing a message - it will specify the <strong>topic</strong> it wants to send the message to, is that right? Does it care about partitions?</p>
  </li>
  <li><p>When a subscriber is running - does it specify its group id so that it can be part of a cluster of consumers of the same topic or several topics that this group of consumers is interested in?</p>
  </li>
  <li><p>Does each consumer group have a corresponding partition on the broker or does each consumer have one?</p>
  </li>
  <li><p>Are the partitions created by the broker, and therefore not a concern for the consumers?</p>
  </li>
  <li><p>Since this is a queue with an offset for each partition, is it the responsibility of the consumer to specify which messages it wants to read? Does it need to save its state?</p>
  </li>
  <li><p>What happens when a message is deleted from the queue? - For example, the retention was for 3 hours, then the time passes, how is the offset being handled on both sides?</p>
  </li>
  </ol>