AWS RDS Aurora - Cross Region Read Replica has both Write and Reader instance?

user_5915500 0
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I noticed when a Cross Region Read Replica was created for my AWS Aurora cluster - it has both a Write and Reader instance (Similar to my Primary which naturally has a writer in addition to a reader instance). In the Cluster Configuration for the Cross Region Replica cluster - I can see this "Replica" cluster indeed has the Replication source tag and its correctly getting all data flowed asynchronously.

Couple of questions I need help understanding this:

  • should a Cross Region Replica have a Writer?
  • Should I write to it in case of a disaster in the source region?

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amazon-rds amazon-web-services
3 Answers

I had to explicitly make the read-replica instance (in replica region) as read_only. Otherwise read-replica accepts writes to it.

user_171073690
user_9993670

I think the name "writer" is a bit misleading.

In the doc for Aurora endpoint:

A cluster endpoint (or writer endpoint) for an Aurora DB cluster connects to the current primary DB instance for that DB cluster. This endpoint is the only one that can perform write operations such as DDL statements. Because of this, the cluster endpoint is the one that you connect to when you first set up a cluster or when your cluster only contains a single DB instance. Each Aurora DB cluster has one cluster endpoint and one primary DB instance.

So the writer instance is the same entity as the primary instance of the cluster.

In the doc for Cross-Region Replication:

When you create a cross-Region read replica for Aurora MySQL by using the AWS Management Console, Amazon RDS creates a DB cluster in the target AWS Region, and then automatically creates a DB instance that is the primary instance for that DB cluster.

For cross region replication, the new cluster (writer instance) will be created.

You don't need to take care of the writer instance. For the disaster recovery, promote read replica.

user_80896600
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