title: Why does AWS RDS Aurora have the option of "Multi-AZ Deployment" when it does replication across different zones already by default?
body: <p>When launching an Aurora instance I have the option of "Multi-AZ Deployment", which it describes as "Specifies if the DB Instance should have a standby deployed in another Availability Zone."</p>
  
  <p>However the Aurora documentation states that Aurora already automatically spreads the database across different availability zones?</p>
  
  <p>Additionally, what is the difference between an Aurora Multi-AZ standby and an ordinary Aurora replica. Is that that an ordinary replica can be read from increasing performance whereas a standby cannot be read from?</p>