Restore backup of a DB from another instance

Yes, you can restore a backup from one RDS instance to another instance. Amazon RDS supports importing MySQL databases by using backup files stored in Amazon S3. You can create a backup of your database, store it in an S3 bucket, and then restore the backup file onto a new or existing RDS DB instance.

To restore from S3, you would use the restore operation that creates a new DB instance from your S3 backup. You'll need to specify parameters such as:

• A unique DB instance identifier for your new instance (like "rds2")
• The S3 bucket name where your backup is stored
• An IAM role that allows RDS to access your S3 bucket
• Database configuration details (instance class, allocated storage, engine version, master username and password)

This will create a separate DB instance with the restored data, allowing you to query and check the data without affecting your original instance (rds1) or its current transactions. The restored instance will be completely independent, making it perfect for your offline data verification needs.

Alternatively, if you created a DB snapshot directly within RDS (rather than exporting to S3), you can restore from that snapshot to create a new DB instance. This process also creates a new, independent instance that you can use for checking data without impacting your production database.
Sources
Amazon RDS examples using AWS CLI - AWS SDK Code Examples
restore_db_instance_from_s3 - botocore 1.42.51 documentation
Tutorial: Restore an Amazon RDS DB instance from a DB snapshot - Amazon Relational Database Service