SAA-C03 practice question: Disaster recovery strategies (1 of 2)
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.
A company runs an internal reporting application on Amazon EC2 with an Amazon RDS for MySQL database in one AWS Region.
For a Regional disaster, the business accepts up to 8 hours of data loss and up to 24 hours to restore service in a second Region.
The application is used only during office hours, and the company wants the lowest-cost disaster recovery strategy that meets these targets.
Which approach should a solutions architect recommend?
Choose one answer.
AA. Use AWS Backup every 4 hours for the instances and database, copy each backup to the second Region, and rebuild from templates in a disaster.
BB. Use AWS Backup to back up the instances and database once a day, copy each backup to the second Region, and rebuild from templates in a disaster.
CC. Run a cross-Region read replica of the database in the second Region, keep AMIs copied there, and launch the application servers in a disaster.
DD. Run a scaled-down copy of the full application in the second Region with a cross-Region read replica, and scale it up in a disaster.
Show the answer and explanation
Answer: A
A. Right: Correct. Backup and restore is the cheapest strategy because nothing runs in the second Region until it is needed. A 4-hour schedule keeps data loss well inside 8 hours, and rebuilding from templates and backups fits within a 24-hour recovery time. Learn more: Backup plan options and configuration (opens in a new tab)
B. Wrong: This is the same low-cost strategy, but a daily schedule means a disaster just before the next backup loses almost 24 hours of data. That breaks the 8-hour limit. AWS Backup can run as often as every hour, so a shorter schedule fixes it. Learn more: Backup plan options and configuration (opens in a new tab)
C. Wrong: This is a pilot light design. Continuous replication gives a much smaller data loss and faster recovery than needed, but the company pays for a database instance running all the time. With 8-hour and 24-hour targets, backups are enough. Learn more: Disaster recovery options in the cloud (opens in a new tab)
D. Wrong: This is warm standby. It can take traffic almost at once, but it keeps servers and a database running in the second Region all the time, which costs more than pilot light. The generous targets do not justify it. Learn more: Disaster recovery options in the cloud (opens in a new tab)
Explanation
Disaster recovery strategies trade cost against recovery point and recovery time. With an 8-hour RPO and a 24-hour RTO, backup and restore is enough, as long as backups run often enough: a daily schedule could lose up to 24 hours of data, while every 4 hours stays within the limit. Pilot light and warm standby recover faster but pay for resources that run all the time.
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