title: store messages of messaging application
body: <p>Actually, I am developing a messaging app and use cassandra as a database and kafka as a message broker.</p>
  
  <p>My question is: 
  Do I need to store the messages between users in cassandra? If I do so, then size of my database will grow really fast. </p>
  
  <p>As I am using a messaging queue, the messages are stored as long as these were not delievered. I have heard, that messaging apps (such as Facebook Messanger, WhatsApp) does not store the message content between users in a database, but only use a queuing system (XMPP, MQTT) which deletes messages as soon as they are delieverd. So no need for storing in external database. Am I right?</p>
  
  <p>What is best practice? Besides, do I need to store the messaging content from the legal perspective (government or the like) for a period of time (for example, 2 years)? </p>
  
  <p>Looking at <a href="http://www.planetcassandra.org/apache-cassandra-use-cases/" rel="nofollow">http://www.planetcassandra.org/apache-cassandra-use-cases/</a>, there are a lot using cassandra as a database backend for messaging apps. However, it is a antipattern to use cassandra as a message-queue (see cassandra docs). </p>