AWS Certified Solutions Architect - Associate
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A company has a multi-tier application that runs six front-end web servers in an Amazon EC2 Auto Scaling group in a single Availability Zone behind an Application Load Balancer (ALB). A solutions architect needs to modify the infrastructure to be highly available without modifying the application.
Which architecture should the solutions architect choose that provides high availability?
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A
Create an Auto Scaling group that uses three instances across each of two Regions.
B
Modify the Auto Scaling group to use three instances across each of two Availability Zones.
C
Create an Auto Scaling template that can be used to quickly create more instances in another Region.
D
Change the ALB in front of the Amazon EC2 instances in a round-robin configuration to balance traffic to the web tier.
Explanation:
Explanation
Correct Answer: B
Why Option B is correct:
- High Availability within a Region: Distributing instances across multiple Availability Zones (AZs) within the same AWS Region provides high availability against AZ-level failures.
- No Application Modification Required: This solution maintains the same application architecture while improving resilience.
- Auto Scaling Group Configuration: By configuring the Auto Scaling group to use three instances across each of two AZs (total of 6 instances), the solution maintains the same total capacity while providing redundancy.
- ALB Integration: The Application Load Balancer can automatically distribute traffic across instances in multiple AZs and handle health checks.
Why other options are incorrect:
A. Create an Auto Scaling group that uses three instances across each of two Regions.
- This creates a multi-region architecture which is more complex and may require application modifications for data synchronization and failover.
- Multi-region deployment typically requires additional components like Route 53 for DNS failover and may involve data replication challenges.
- This is overkill for achieving high availability within a single region.
C. Create an Auto Scaling template that can be used to quickly create more instances in another Region.
- This only provides a template for disaster recovery but doesn't implement active high availability.
- The infrastructure would still be vulnerable to AZ failures in the primary region.
- This is a reactive approach rather than a proactive high availability solution.
D. Change the ALB in front of the Amazon EC2 instances in a round-robin configuration to balance traffic to the web tier.
- Round-robin configuration is a load balancing algorithm, not a high availability solution.
- This doesn't address the single point of failure issue of having all instances in one Availability Zone.
- The ALB already performs load balancing; changing the algorithm doesn't improve availability.
Key AWS Concepts:
- Availability Zones (AZs): Physically separate data centers within an AWS Region with independent power, cooling, and networking.
- High Availability: The ability of a system to remain operational even when some components fail.
- Multi-AZ Deployment: Distributing resources across multiple AZs protects against AZ-level failures.
- Application Load Balancer (ALB): Can distribute traffic across instances in multiple AZs and perform health checks to route traffic only to healthy instances.
Best Practice: For high availability, always distribute resources across at least two Availability Zones within a Region to protect against AZ-level failures.
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