AWS Certified Advanced Networking Specialty Practice Exam

For a mission-critical application needing low latency, which is not considered a best practice for high availability?

1. Use multiple Availability Zones

2. Implement auto-scaling

3. Use a placement group for guaranteed low latency

4. Enable health checks for your instances

The correct answer is: Use a placement group for guaranteed low latency

Using a placement group for guaranteed low latency is not considered a best practice for high availability, particularly in the context of a mission-critical application. Placement groups can provide low latency by ensuring that instances are physically located close to one another within the same Availability Zone. However, this clustering approach can compromise high availability. If there’s a failure in that particular Availability Zone, all instances in the placement group may become unavailable, leading to significant downtime for the application. In contrast, utilizing multiple Availability Zones, implementing auto-scaling, and enabling health checks are all strategies designed to enhance availability. Deploying applications across multiple Availability Zones helps ensure that even if one zone experiences an issue, the application can still function using instances in other zones. Auto-scaling provides the ability to adjust capacity dynamically based on demand, which contributes to maintaining performance and availability during varying loads. Health checks allow for the automatic detection of unresponsive instances, which can then be replaced or restarted without manual intervention, further promoting high availability. Thus, while placement groups are useful for latency, relying solely on them does not align with best practices for ensuring high availability in mission-critical applications.