Simple Notification Service (SNS)
Kinesis + MQ
Databases & Analytics
RDS Read Replicas
  • Multiple database engines have built-in replication functionality to create a special type of database instance called a read replica from a source database instance.
  • The source DB instance becomes the primary database instance.
  • Updates made to the primary database instance are asynchronously copied to the read replica.
  • You can reduce the load on your primary database instance by routing read queries from your applications to the read replica.
  • You can promote a read replica into a standalone database instance.
    • When you promote a read replica, the database instance is rebooted before it becomes available.
  • The following are where read-replicas are useful:
    • Scaling beyond the compute or I/O capacity of a single DB instance for read-heavy database workloads.
      • You can direct this excess read traffic to one or more read replicas.
    • Serving read traffic while the source database instance is unavailable.
      • In these cases, you can direct read traffic to your read replicas.
        • For this use case, keep in mind that the data on the read replica might be "stale" because the source database instance is unavailable.
    • Business reporting or data warehousing scenarios.
      • You might want business reporting queries to run against a read replica, rather than your production database instance.
    • Implementing disaster recovery.
      • You can promote a read replica to a standalone instance as a disaster recovery solution if the primary database instance fails.
  • Data goes from 1 AZ to another = Data Charges.
  • Data stays in the same AZ = Free.
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