Multi AZ DB Instance

• We get a Master DB Instance and a Standby DB Instance
• Automatic failover is enabled
  
• We will have a single endpoint which is readwrite endpoint

Multi AZ DB Cluster

• Creates a DB cluster with a primary DB instance and two readable standby DB instances
  
• We will get a read endpoint as well as write endpoint
  
  

Read Replicas

• AWS Allows us to create read replicas of any database instance and it gets a read endpoint in any region.
• Here the replication is asynchronous in nature. the delay will be in seconds (at max)
• Read Replica can be promoted which means we can start writing data into it, but promotions stops replication from Main instance
• For non-critical applications
  • We create a single db instance (read write endpoint)
  • We create a read replica (read endpoint)
• For creating read replicas enabling backups is mandatory.

Exercise

• Create a free tier mysql rds single instance in region-a, Ensure while creating you donot disable backups
• Now select action and create a read replica in region-b
• Now insert some data in region a and query in region b using SQL Client (Azure Data Studio or mysql cli)