Exams / SAA-C03 / RDS Multi-AZ / Question 1
SAA-C03 practice question: RDS Multi-AZ
Design Resilient Architectures A free question from our original SAA-C03 practice exam. Try it, then open the answer to see why each option is right or wrong.
An insurance company runs its policy administration system on a Single-AZ Amazon RDS for PostgreSQL DB instance. After a recent Availability Zone outage, the business set new targets: the database must fail over automatically within a few minutes, and no committed transaction may be lost. Reporting already runs on a separate data warehouse, so a standby does not need to serve reads. Which solution meets these requirements MOST cost-effectively?
Choose one answer.
- AA. Convert the DB instance to a Multi-AZ DB instance deployment, so that RDS keeps one synchronous standby in another Availability Zone.
- BB. Convert to a Multi-AZ DB cluster deployment, with one writer and two readable standby instances in three Availability Zones.
- CC. Create a read replica in another Availability Zone, and use an RDS event notification and a Lambda function to promote it after a failure.
- DD. Keep automated backups with point-in-time recovery, and script a restore to a new DB instance in another Availability Zone after a failure.
Show the answer and explanation
Answer: A
- A. Right: Correct. The standby is updated synchronously, so committed transactions are not lost, and RDS fails over to it automatically, typically in 60 to 120 seconds. It runs one extra instance, the least needed for automatic failover. Learn more: Multi-AZ DB instance deployments (opens in a new tab)
- B. Wrong: A Multi-AZ DB cluster commits only after at least one reader acknowledges the change, and it fails over automatically, so it meets the targets. But it runs three DB instances, and the extra readable standby is something the company said it does not need. A Multi-AZ DB instance deployment meets the targets for less. Learn more: Multi-AZ DB cluster deployments for Amazon RDS (opens in a new tab)
- C. Wrong: Read replicas are updated asynchronously, so transactions committed just before the failure may not have reached the replica. The promotion logic is also custom code that the team must maintain. Multi-AZ replicates synchronously and fails over without custom automation. Learn more: Working with DB instance read replicas (opens in a new tab)
- D. Wrong: Point-in-time restore usually reaches only to within the last five minutes, so recent transactions can be lost. The restore also creates a new instance with a new endpoint, which takes far longer than a few minutes for a large database. It is cheap, but it misses both targets. Learn more: Backup and recovery for Amazon RDS (opens in a new tab)
Explanation
Zero data loss needs synchronous (or semisynchronous) replication, and failover within minutes needs it to be automatic. Both Multi-AZ options meet that; read replicas and backups do not. Because the standby does not need to serve reads, the single-standby Multi-AZ DB instance deployment is the cheaper fit.
Study
Keep practising
Answer questions with a score at the end, or practise just this topic with the explanation after each one. No sign-up needed.