Exam AWS Certified Solutions Architect - Associate SAA-C02 topic 1 question 255 discussion

A. Application Load Balancer is region based, so this ain't right.https://aws.amazon.com/elasticloadbalancing/ B. We can use Route 53 for a Region failover, but, why create a read replica? we need a snapshot. C. Sounds fishy using a read replica again. D. Sounds about right, we create a snapshot of the RDS instance, and replicate the snapshot for a backup Region.

If I understand correctly, read replicas can be done in multiple regions, but they are not a suitable backup tool but are only used to improve performance. Then you delete the B and C. Application Load Balancer works only within a region then you delete the A. D is correct.

B is the answer

D LEAST EXPENSIVE

D seems ok.

D LEAST EXPENSIVE https://aws.amazon.com/blogs/database/implementing-a-disaster-recovery-strategy-with-amazon-rds/

@lc76262 You clearly do not understand what RPO is. It represents the data that you can lose, it is orthogonal to time to recover. You can take 3 weeks to recover, that wouldn't change the RPO. Right answer is obviously D.

BBBBBBBBBBBBB Replicating backup snapshot on daily basis to other region is not cost effective solution so D is wrong

D is wrong. For example, if you take a snapshot at 1 AM tomorrow and there is a disaster while your snapjob was running. You only have the previous day's backup (more than 24 hours ago). You cannot obviously meet the RPO of 24 hours in this scenario. For experienced DBAs, snapshots are not sufficient to restore a database because you need the redo logs for recovery.

D is wrong logically due to "RTO = 3 hours and RPO is 24 hours." If you only backup your database once a day, it might take some time plus the time to recover, the RPO of 24 hours will not be met. To met the RPO of 24 hours, you need to backup at least twice daily. Moreover, copying a snapshot of the entire database will cost more in bandwidth than the smaller changes to the database for the replica.

B is correct. You use read replicas to improve performance, not mainly for DR. RTO is the key here, 24 hours.

but if i'm not wrong between regions a snapshot must be copied, not replicated.

I would pick D https://aws.amazon.com/blogs/database/implementing-a-disaster-recovery-strategy-with-amazon-rds/: Table displayed shows read replicas having the highest cost for recovery A is not cost effective ("Deploy separate RDS instances in each Region") B and C are out since read replicas are used

Base on lowest cost. it's D in the official matrix of AWS https://aws.amazon.com/blogs/database/implementing-a-disaster-recovery-strategy-with-amazon-rds/

As per below; https://aws.amazon.com/blogs/aws/cross-region-read-replicas-for-amazon-rds-for-mysql/ You can now create cross-region read replicas for Amazon RDS database instances! This feature builds upon our existing support for read replicas that reside within the same region as the source database instance. You can now create up to five in-region and cross-region replicas per source with a single API call or a couple of clicks in the AWS Management Console. We are launching with support for version 5.6 of MySQL.

B and D serves the purpose. But D is the most cost effective. The data transferred for cross-Region replication incurs Amazon RDS data transfer charges. These cross-Region replication actions generate charges for the data transferred out of the source AWS Region. And for each data modification made in the source databases, Amazon RDS transfers data from the source AWS Region to the read replica AWS Region.

D. Lowest cost