AWS Auto Scaling Interview Q/A

What is AWS Auto-Scaling and how does it work?

AWS Auto-Scaling is a service that automatically adjusts the capacity of your resources to match changing workloads. It works by monitoring performance metrics and, based on predefined policies, it can increase or decrease resources such as EC2 instances or ECS tasks to maintain desired performance levels, all while minimizing idle resource costs.

Does AWS Autoscaling Work?

Yes, AWS Autoscaling works effectively by monitoring application performance and dynamically scaling resources to meet demand. It helps ensure the right resource levels while minimizing idle costs, making it especially useful for applications with variable workloads.

Define Auto Scaling. Auto Scaling is a technique for automatically adjusting system capacity to meet changing workloads, commonly used in cloud environments like AWS. Policies are defined to trigger resource scaling based on conditions like CPU utilization, helping optimize performance and costs.

What is the difference between a single instance Web environment and Load-Balanced Auto-Scaling? A single-instance web environment uses only one instance to handle traffic, while Load-Balanced Auto-Scaling employs multiple instances behind a load balancer. The latter provides high availability, redundancy, and better handling of variable workloads.

On an EC2 instance, an application of yours is active. Once the CPU usage on your instance hits 80%, you must reduce the load on it. What strategy do you use to complete the task?

To reduce the load on the instance, you can configure auto-scaling policies to trigger when CPU usage exceeds 80%. These policies may add more instances to share the load or reduce instances if the usage drops below the threshold, effectively balancing the load.

Explain the auto-scaling feature of EC2 along with its benefits.

EC2 auto-scaling allows you to automatically adjust the number of instances based on metrics like CPU usage. This ensures your application can handle varying workloads efficiently and cost-effectively. Benefits include improved performance, high availability, and reduced operational effort.

Can you change the instance type of the instances that are running in your application tier and are also using autoscaling? If yes, then how?

Yes, you can change the instance type of instances in an auto-scaling group. To do this, you would create a new launch configuration or update the existing one with the desired instance type. Then, you update the auto-scaling group to use the new launch configuration.

I created a web application with autoscaling. I observed that the traffic on my application is the highest on Wednesdays and Fridays between 9 AM and 7 PM. What would be the best solution for me to handle the scaling?

To handle this specific traffic pattern, you can create scheduled auto-scaling actions that increase the instance count on Wednesdays and Fridays between 9 AM and 7 PM. This ensures your application can handle the peak traffic during those hours and scale back down during off-peak times.

You have an application running on your Amazon EC2 instance. You want to reduce the load on your instance as soon as the CPU utilization reaches 100 percent. How will you do that?

To reduce the load when CPU utilization hits 100 percent, you can configure an auto-scaling policy to trigger when CPU usage exceeds a specified threshold. This policy can then reduce the number of instances or terminate instances, effectively distributing the load and preventing performance issues.

What is Amazon EC2 Auto Scaling?

Amazon EC2 Auto Scaling is a service that automatically adjusts the number of EC2 instances in response to changes in demand. It helps maintain application performance, availability, and cost-efficiency by dynamically scaling resources up or down based on predefined policies.

What is the Pricing for Amazon EC2 Auto Scaling?

Amazon EC2 Auto Scaling itself is a free service. However, you are charged for the EC2 instances, Amazon RDS, or other resources that you use within the auto-scaling groups. The pricing for these resources depends on their individual pricing models.

How do Auto Scaling groups work?

Auto Scaling groups are a key component of EC2 Auto Scaling. They define the desired capacity, launch configurations, and scaling policies for your instances. These groups automatically create and manage instances, ensuring that the application scales up or down as required.

What are Auto Scaling components?

Auto Scaling components include Auto Scaling groups, launch configurations, scaling policies, and scaling triggers. Auto Scaling groups define the number and type of instances, launch configurations specify instance configurations, scaling policies set scaling rules, and triggers define the conditions that trigger scaling actions.

What are Auto-Scaling Related Services?

Auto-scaling-related services in AWS include Amazon CloudWatch for monitoring and setting alarms, Elastic Load Balancing for distributing traffic across instances, and AWS Application Auto Scaling for scaling resources other than EC2 instances, such as ECS tasks and DynamoDB tables. These services complement and enhance auto-scaling capabilities.

What is Application Auto Scaling in AWS?

AWS Application Auto Scaling is a service that allows you to automatically adjust the capacity of various AWS resources beyond just EC2 instances. You can use it to scale resources like Amazon ECS tasks, Amazon DynamoDB tables, and more. This service helps you optimize the performance and cost of these resources based on defined scaling policies and metrics.

What are scaling policies in AWS Auto Scaling?

Scaling policies in AWS Auto Scaling are rules that define how the service should adjust the number of instances or resources based on specified conditions. These policies can scale resources out (increase capacity) or (decrease capacity) to maintain desired performance levels and control costs.

How can you configure Auto Scaling to handle sudden spikes in traffic?

To handle sudden traffic spikes, you can configure auto-scaling policies with more aggressive scaling triggers, lower cooldown periods, and larger scaling increments. Additionally, you can use scheduled scaling actions to anticipate expected traffic increases during specific times.

Can you give an example of an AWS service that complements Auto Scaling to improve availability?

Elastic Load Balancing (ELB) is an AWS service that complements Auto Scaling by distributing incoming traffic across multiple instances. It enhances availability by ensuring that traffic is directed to healthy instances, making your application more fault-tolerant.

What is the cooldown period in Auto Scaling?

The cooldown period in Auto Scaling is a time interval during which the service prevents any further scaling actions after a scaling activity has occurred. It helps stabilize the environment by avoiding rapid, consecutive scaling events that could be triggered by fluctuating metrics.

How does Auto Scaling handle instances that fail to launch successfully?

Auto Scaling has a feature called "Instance Protection" that can be used to handle instances that fail to launch successfully. By setting instance protection for specific instances, Auto Scaling will not terminate or replace those instances if they fail to launch, preventing unnecessary scaling actions.

What are the benefits of using Amazon CloudWatch with Auto Scaling?

Amazon CloudWatch is used to monitor the performance of resources in Auto Scaling. It provides detailed metrics and the ability to set alarms based on those metrics. This helps in real-time monitoring and automatic scaling based on specified thresholds, ensuring optimal application performance.

How can you ensure that Auto Scaling does not scale down to zero instances, leaving the application unavailable?

To ensure that Auto Scaling never scales down to zero instances, you can set a minimum desired capacity in your Auto Scaling group. This way, even during periods of low demand, there will always be a minimum number of instances running to keep the application available.

What is the difference between scaling out and scaling in Auto Scaling?

Scaling out in Auto Scaling refers to increasing the number of instances or resources to handle increased demand. Scaling in, on the other hand, involves reducing the number of instances or resources when demand decreases to save costs and avoid overprovisioning.

What is the significance of an Amazon Machine Image (AMI) in Auto Scaling?

An Amazon Machine Image (AMI) is a template for creating EC2 instances. In Auto Scaling, you specify an AMI for your launch configuration. When Auto Scaling adds new instances, it uses the specified AMI to create them, ensuring that all instances in the group are consistent and configured identically.