AWS Series — Optimize your database with RDS Read Replicas
AWS offers relational databases on cloud providing 6 options to choose from based on our need. To know more about RDS. Click below —
AWS Series — Relational Database in AWS
Now let us see how we can increase Read Performance using Read Replicas.
What is Read Replica?
It is the Read-only copy of your primary database.
Great for read-heavy workloads and takes the load off your primary database.
Multi-AZ is of disaster recovery and Read Replica is for boosting performance
Read-Replica can also be in cross - AZ or cross-region. So you can put them in a completely different region in a completely different part of the US or part of the world. It will replicate across to that region automatically. But this is not used for disaster recovery and only used for performance.
Each Read replica has its own DNS endpoint.
If we lose your primary and it fails over to the secondary, Amazon basically updates the DNS endpoint to point to IP address.
With Read Replicas, you actually get your own unique DNS endpoint. You will have 1 for primary and other one for replica and read replicas can be promoted to be their own databases.
We can have a read replica and promote it to make it independent database. This breaks the replication so there is no more replication between the databases but then you could connect up a business intelligence server to that database and run all queries. This can be used for analytics processing and if you are about to do a massive query towards your database.
Summary —
- Scaling Read Performance — Primarily used for scaling, not for disaster recovery
- Requires Automatic Backup — Automatic backups must be enabled in order to deploy a read replica
- Multiple Read Replicas are Supported — MySQL, MariaDB, PostgreSQL, Oracle and SQL Server allow you to add up to 5 read replicas to each DB instance.
Let us see how we can provision this.
Go to AWS Management Console > RDS > Create Database > Select the database created > Actions > Create Read Replica
Give the DB Instance Identifier which should be unique and select the type of DB instance class.
Select the AWS region and Storage required for you read replica.
Select the Availability where you would like to replication to be enabled.
Select the networking like subnet and VPC.
Then create the read replica.
As you can see in UI designs it is connected to original database. We can select the database replica and go to actions and click promote, which will create it as independent primary database.
We can also turn on backups. It depends on the use case you need this replica for.
What is the difference between Multi AZ and Read Replica?
Happy Learning!!
