ELB Auto Scaling

5 minutes 5 Questions

Auto Scaling is a feature that automatically adjusts the number of registered instances in an Elastic Load Balancer target group based on real-time demand, ensuring optimal workload distribution and availability. It supports both scale-out and scale-in operations, increasing or decreasing the number of instances in response to predefined scaling policies, such as traffic thresholds or the average CPU utilization of target instances. Auto scaling helps maintain high availability and automatically handles changing application requests, resulting in an efficient, cost-effective solution by distributing traffic across the most appropriate resources.

Guide to ELB Auto Scaling

Elastic Load Balancing (ELB), combined with Auto Scaling, is a critical component for AWS solution architects to ensure the reliability, availability, and scalability of AWS cloud applications.

What is ELB Auto Scaling?
ELB distributes incoming application traffic across multiple targets, such as EC2 instances, which are automatically scaled up or down by the Auto Scaling feature based on defined conditions.

Why is it important?
ELB Auto Scaling helps in distributing workload evenly across servers, preventing resource over-utilization, and ensuring high availability and fault tolerance of your applications.

How it works:
When a predefined condition is met, such as CPU utilization exceeding 70 percent, Auto Scaling dynamically adjusts the number of instances in response. These instances are automatically registered with the load balancer.

Exam tips:
When answering questions on ELB Auto Scaling in an exam, keep in mind that it's not just about scaling instances, but also about evenly distributing workload and optimizing resource use. Be aware that Auto Scaling applies to instances in an Availability Zone, not across multiple zones, and that ELB automatically registers and de-registers instances without manual intervention.

Remember, ELB and Auto Scaling are designed to work together to help maintain the availability of your application during demand spikes and traffic fluctuations, which is a theme that commonly appears in the exam.

Test mode:

Exam (Timed)

Practice (With explanations)

Start practice test

Question 1

You have a web application running on EC2 instances in an Auto Scaling group (ASG) with an attached Classic Load Balancer (CLB). The instances are taking longer to provision, leading to slow scaling. What would be the BEST way to speed up scaling?

Configure the ASG to use scheduled scaling. Enable multi-AZ deployments for the ASG. Use an Application Load Balancer (ALB) instead of a Classic Load Balancer. Use Amazon Machine Images (AMIs) with the application pre-installed.

Correct Answer: Use Amazon Machine Images (AMIs) with the application pre-installed.

Using AMIs with the application pre-installed will decrease the time required for instance provisioning, allowing faster scaling. Switching to an ALB from a CLB doesn't affect scaling. Enabling multi-AZ deployments and termination protection don't address the root cause of the problem. Scheduled scaling can be helpful, but it may not address rapid scaling needs. Reducing Desired Capacity contradicts the need for scaling.

Question 2

A web application is deployed across two availability zones using an Application Load Balancer (ALB) and Auto Scaling groups. The ALB latency suddenly increases, causing client errors. What is the BEST way to resolve this issue?

Migrate the application to a single availability zone. Enable Sticky Sessions on the ALB to bind user sessions to specific instances. Decrease the health check interval for the ALB. Switch from an ALB to a Network Load Balancer.

Correct Answer: Enable Sticky Sessions on the ALB to bind user sessions to specific instances.

Enabling Sticky Sessions on the ALB helps to bind user sessions to specific instances, reducing latency and session-related errors. Switching to a Network Load Balancer wouldn't help, as it does not support sticky sessions. Decreasing the health check interval would not resolve the latency issue. Migrating the application to a single availability zone can compromise fault tolerance. Increasing the idle timeout value and using SSL offloading do not address the root cause of the problem.

Question 3

An application is running on EC2 instances in an Auto Scaling group with a Classic Load Balancer (CLB). A new version of the application has been developed. What would be the BEST method to deploy the new version without causing downtime?

Use an Application Load Balancer instead of a Classic Load Balancer. Terminate instances running the older version and launch instances with the new version. Use a Blue/Green deployment strategy with two Auto Scaling groups. Change the instance type of the existing instances to support the new version.

Correct Answer: Use a Blue/Green deployment strategy with two Auto Scaling groups.

A Blue/Green deployment strategy with two Auto Scaling groups allows the new version to be tested before switching traffic, ensuring zero downtime. Terminating instances and launching new ones can cause downtime. Changing the instance type or switching to an ALB doesn't address the requirement for zero downtime. Deploying the new version to all instances simultaneously can cause issues and potential downtime. Scheduled scaling isn't relevant to this scenario.

Go Premium