AWS Interview Questions: EC2

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  • September 2, 2021
  • AWS

What is EC2?

EC2 is abbreviation for Elastic Compute Cloud. It’s one of the most used services in AWS cloud. It offers businesses a platform for creating virtual machines On-Demand without any upfront cost in AWS datacentre. The underlying infrastructure for hosting the virtual machine is maintained and managed by AWS. With EC2, AWS provides highly available, secure, reliable, simple and automatically scaling infrastructure.

 

What is EC2 Instance?

EC2 Instance is Amazons terminology for the virtual machine created on AWS Cloud. Organizations across the world host EC2 Instance’s to run workload on them to reduce the cost of ownership of infrastructure. EC2 instances are available on-demand and support convenient pay-as-you-go payment model.

 

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What is a Spot Instance?

Amazons EC2 Spot Instances allows organizations to take advantage of unused computing in AWS EC2 at a very discounted and attractive cost. Organizations can use spot instances with up to 90% cheaper cost compared to on-demand instances. Spot instances can be used for applications such as web servers, containerised workloads, CI/CD, high performance computing (HPC), testing and development. The best feature of spot instance is that its ability to get combined with reserved instances, on-demand instances and saving plan instances. AWS gives a notice of two minutes before reclaiming the capacity and mean-while users owning them can stop, terminate or hibernate them.

 

Explain the stages of creating EC2 Instance.

Creating an EC2 instance is very simple and almost anybody can very easily provision one. First select the EC2 service in AWS Management Console and navigate to the appropriate AWS region where the instance needs to be created. Then select the Instances option from the left side options pane and then click on the launch instances button and the instance creation wizard start. Select an appropriate AMI and then in the next section select the instance size according to your requirement and then click Configure Instance Details. Here, you get to configuration options such as number of instances, network setting, placement group, domain join, etc. that you would configure according to your needs. Next click on Add Storage and you would get the options to setup the storage as per the needs of your instance. At the next step you configure tags for the instance. Lastly you are provided with options to open ports for your applications in the Security Group. Review your configuration and finally click the Launch button, where you will require to select the Key that you want to associate with your instance. Acknowledge that you possess the private key and finally click on Launch Instance. Depending on your selected AMI and other configuration options, you may need to wait some time and the instance should be created very quickly.

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Explain the difference between Public IP and EIP.

Public IP: It is a usual Public IP Address that is associated to EC2 instance. With this address the instances can host resources on internet. If an instance is stopped, the associated Public Address is released and once the instance starts again, a new Public Address is issued resulting in updating the host record on DNS Server.

EIP: Elastic IP Address is a static Public Address that’s associated to EC2 instance. EIP will not change even if a server is stopped and started again. This address also allows a instance to host resources on public internet very similar to Public Address.

 

What is EBS volume?

EBS (Elastic Block Store) is a virtual block device that can be attached to EC2 instance. In simple language it’s a virtual hard disk attached to EC2 instance. The EBS store can start from a minimum capacity of 1GiB and can extend to a maximum limit of 16TiB. 

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What are root device volume?

In the easiest way, it can simply be explained as a EBS volume that is created from a EBS snapshot that is associated to an AMI. It is the boot volume of your instance and contains the operating system, applications and configuration. General Purpose, Provisioned IOPS and Magnetic Volumes can only be used as root device volume with EC2 instances.

 

Explain EBS Snapshots.

Amazon defines EBS Snapshots as incremental backup of EBS Volumes. Organizations can create snapshot of EBS volume, as they can restore the volume and data in case some data is lost or gets corrupt. EBS Snapshots are stored in S3 buckets managed by AWS.  

 

What is AWS EC2 Placement Group?

To minimize the risk of correlated hardware failures, one can use a tool called Placement Group that strategically places the highly-available EC2 instances across different physical server that may be a part of different partitions or even availability zones.

 

What is a Security Group?

You can imagine security group as a software firewall that is compulsorily attached to the network interface of a EC2 instance. Security Group provides “stateful” filtering. Security Group can be attached to multiple network interfaces of EC2 instances belonging to the same VPC. A user can define exceptions for traffic on inbound and outbound directions on the network interface. By default, all traffic is denied, a user can only create exceptions for traffic that should be permitted.

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Explain the concept of Auto Scaling.

Auto Scaling is one of the important feature offered by EC2. With auto scaling, organizations can maintain consistent application delivery to their consumers. Auto scaling helps organizations to automatically add or remove EC2 instances, and maintain a desired amount of compute to service the changing demand. The instance fleet management feature not just only help organizations to scale compute horizontally as per changing demand, but also allows them to cut upon the cost. 

 

Describe AWS Elastic Load Balancer.

To ensure continuous delivery of our applications, Amazon provides us with Elastic Load Balancer with EC2, that can automatically distribute traffic to our application across multiple targets such as instances, lambda functions, virtual appliances, IP address and containers. Elastic Load Balancer can distribute the application traffic to targets hosted in a single availability zone or distributed across multiple availability zones. Elastic Load Balancer is a virtual load balancer and is available in four distinct models and each of them offers high availability across different availability zones, automatic scaling support and reliability to ensure our applications are fault tolerant.

 

Author”-

 Shaikh, Aftab | SevenMentor Pvt Ltd.

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