An application currently runs in a single Availability Zone. Which approach is MOST appropriate for improving availability so that service continues even if an AZ failure occurs?
Identify the high-availability design approach that keeps service running through an AZ failure.
Increase the number of instances within the same AZ.
An Availability Zone (AZ) is a grouping of one or more data centers within a Region, each with independent power and networking. Adding more instances within the same AZ helps with load distribution, but if that entire AZ fails, all instances stop simultaneously.
Distributing across multiple AZs is required to tolerate an AZ failure, so this approach does not meet the requirement.
Change the instance type to a larger size.
Upgrading to a larger instance increases processing capacity, but the instance remains in a single AZ.
If an AZ failure occurs, that instance stops, so this approach does not improve availability.
Take daily backups of the instances.
Backups are effective for recovering from data loss, but restoration takes time.
This approach cannot meet the requirement of keeping the service running at the moment an AZ failure occurs.
Distribute instances across multiple Availability Zones.
Correct. Distributing instances across multiple AZs and using a load balancer means that even if one AZ fails, instances in the other AZs continue serving traffic. This is the foundational pattern for high-availability design.
'Service continuity through an AZ failure' and 'high availability' call for Multi-AZ distribution + a load balancer. Adding instances within a single AZ, upgrading instance size, and taking backups all fail to survive an AZ-level outage.