Multi-availability zone architecture can provide redundancy for a more resilient database infrastructure. RDS instances can be configured in clusters that cross availability zones for MySQL and PostgreSQL database engines. For more information, see the AWS documentation.
References:
https://docs.aws.amazon.com/AmazonRDS/latest/UserGuide/create-multi-az-db-cluster.html
In AWS Console -
In Terraform -
References:
https://registry.terraform.io/providers/hashicorp/aws/latest/docs/resources/db_instance#multi_az