title: cassandra connections spikes load issue
body: <p>I am using cassandra according to the following struct:
  21 nodes , AWS EC2 i3.2xlarge , version 3.11.4 .</p>
  
  <p>The application is opening about 5000 connection per node (so its 100k connections per cluster) using the datastax java connection driver.
  Application is using autoscale and frequently opens/close connections.
  Number of connections to open at once by app servers can reach up to 500 per node (opens simultaneously on all nodes at once - so its 10k connections opens at the same time across the cluster)</p>
  
  <p>This cause spikes of load on cassandra and cause reads and writes latency.
  I have noticed each time connections opens/close there are high number of reads from system_auth.roles and system_auth.role_permissions.</p>
  
  <p>How can I prevent the load and resolve this issue ?</p>