Most Asked Interview Questions and Answers on AWS Auto Scaling Groups (ASG)

What is an AWS Auto Scaling Group (ASG) and what is its purpose?

An AWS Auto Scaling Group (ASG) is a collection of Amazon EC2 instances that are managed as a group to ensure that the number of running instances automatically adjusts based on the specified policies, helping to maintain application availability and performance while optimizing costs.

How do you configure scaling policies for an Auto Scaling Group?

Scaling policies can be configured using CloudWatch alarms to trigger scale-out or scale-in actions. You can define policies based on metrics such as CPU utilization, memory usage, or custom metrics, and set thresholds to scale the number of instances up or down as needed.

Explain the difference between a Launch Configuration and a Launch Template.

A Launch Configuration is a template used to create EC2 instances with specific settings, such as instance type and AMI. A Launch Template is a more flexible and feature-rich alternative, allowing you to create multiple versions with different configurations, and supports advanced features like parameterized inputs and default values.

What is the role of Elastic Load Balancing (ELB) with Auto Scaling Groups?

ELB works with Auto Scaling Groups to distribute incoming traffic across the instances in the group. When instances are added or removed, ELB automatically updates its target group to ensure traffic is directed to healthy instances, helping to maintain high availability and performance.

How do you ensure instances launched by an ASG are evenly distributed across multiple Availability Zones?

You can configure your Auto Scaling Group to span multiple Availability Zones by specifying the desired zones when creating the group. AWS Auto Scaling will then distribute instances across these zones to ensure high availability and fault tolerance.

What are the key components of an Auto Scaling Group?

Key components include the Launch Configuration or Launch Template, Auto Scaling Policies, Scaling Triggers (such as CloudWatch alarms), and the desired, minimum, and maximum number of instances.

How does AWS Auto Scaling handle health checks?

AWS Auto Scaling uses health checks to determine if instances are healthy. It can use EC2 status checks or ELB health checks. If an instance is deemed unhealthy, ASG automatically replaces it with a new instance to maintain the desired capacity.

Can you explain how to use Scheduled Actions with Auto Scaling Groups?

Scheduled Actions allow you to automatically scale your Auto Scaling Group based on a specific time or date. For example, you can schedule scaling activities to increase capacity during business hours and decrease capacity during off-hours, optimizing costs and performance.

What are the differences between Scaling Policies, Scheduled Actions, and Dynamic Scaling?

Scaling Policies are used to adjust the number of instances based on real-time metrics and alarms. Scheduled Actions are used for scaling based on predefined schedules. Dynamic Scaling adjusts capacity automatically in response to changing demand, based on metrics and thresholds.

How do you troubleshoot issues with Auto Scaling Groups?

Troubleshooting involves checking the Auto Scaling Group’s configuration, reviewing CloudWatch metrics and alarms, analyzing scaling policies and triggers, verifying instance health checks, and reviewing Auto Scaling Group activity logs for error messages or issues.