AWS Interview Questions

1. What is AWS?

AWS [Amazon web services] is one of the popular cloud providing platform by Amazon. It offers more than 200+ fully featured services.

2.Why to use cloud instead of on premise?

• Cloud – On demand resource provisioning. 
• Increase speed
• Cost effective 

3. State the layers available in cloud computing.

The following are the layers available in cloud computing:

Infrastructure-as-a-Service (IaaS): IaaS is the basic layer of infrastructure for instant computing in cloud IT. It facilitates services such as storage resources and provides access to networking tools over the internet.

Platform-as-a-Service (PaaS): PaaS is a cloud computing model that provides an environment for the deployment of applications in the cloud. It provides services and stacks for the deployment of applications. The platform it provides gives services such as databases and operating systems.

Software-as-a-Service (SaaS): SaaS is a computing platform that makes it possible to deliver applications via the internet. In other words, SaaS allows users to access applications through web browsers.

4. What is Amazon EC2?

Amazon elastic compute is a cloud server that enables secure, resizable compute capacity in the cloud. It comes under cloud compute domain.

5. What are the different types of EC2 options available in AWS?

Different EC2 options present are as under:

• OnDemand
• Reserved
• Spot
• Dedicated Hosts.

6. What is S3 in AWS?

It is a Simple Storage Service. It is also called Object storage. We can store large objects using a Key-value approach.  

7. How can you send a request to Amazon S3?

Amazon S3 is a REST service, and you can send a request by using the REST API or the AWS SDK wrapper libraries that wrap the underlying Amazon S3 REST API.

8. Explain what T2 instances are?

T2 instances are designed to provide moderate baseline performance and the capability to burst to higher performance as required by the workload.

9. Explain how the buffer is used in Amazon web services?

The buffer is used to make the system more robust to manage traffic or load by synchronizing different components. Usually, components receive and process the requests in an unbalanced way. With the help of a buffer, the components will be balanced and will work at the same speed to provide faster services.

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10. What is a snowball?

Snowball is a petabyte-scale data transport solution that uses secure appliances to transfer large amounts of data into and out of AWS Cloud.

11. What is CloudFront?

It is a CDN service – Content delivery network service built for high performance, security, and developer convenience. 

12. What is SNS?

It is Simple notification service that provides message delivery to multiple subscribers.

13. What is EFS?

Amazon EFS is an Elastic file system. It is used to deliver file storage to the hundreds of clients simultaneously.

14. What is a VPC?

VPC (Virtual private cloud) is used to set up a logically separate data center in the cloud which can be used to distinguish your AWS service from services which are hosted by other users. Once we set up a VPC we have to provide an IPv4 address range which can be used by resources hosted in it. The IP range can be from \16 to \28.

15. What is CloudWatch?

AWS CloudWatch is a tool to monitor applications and manage their resources. This allows you to have a metric report of the performance of your applications in real-time. Also, it allows you to track other Amazon web services in the form of stats and graphical reports, thus assisting you in configuring all your AWS services within the console.

Amazon Web Services provides 2 types of CloudWatch:

• Basic monitoring: Basic monitoring is available by default in AWS CloudWatch on the launch of an instance. In general, CloudWatch requires five minutes to collect monitoring data.
• Detailed monitoring: To get detailed monitoring of the instances, you have to enable it explicitly. Detailed monitoring CloudWatch takes up to a period of one minute to collect data.

16. What is a subnet?

Once we are done with setting up the VPC, we can spin up multiple subnets in the VPC. The number of subnets we can initiate depend on the number of availability zones in that particular region. One subnet spans only a single AZ. The IP addresses range assigned to a subnet is a subset of the parent VPC’s IP address range. Any two subnets cannot overlap the IP addresses among themselves. The VPC is used to set up public and private instances.

17. What is the difference between a public and private subnet?

Instances present in the public subnet can be accessed from the internet while we cannot access the resources present in the private subnet. We can make a public subnet by sending out traffic using Internet Gateway in the route table from the subnet.

18. What is an internet gateway?

An Internet Gateway is a logical connection between an Amazon VPC and the Internet. It is not a physical device Only one can be associated with each VPC. It does not limit the bandwidth of Internet connectivity. 

19. Can a subnet span across multiple Availability zones?

No. A subnet cannot span across multiple availability zones.

20. What is an ENI?

An elastic network interface is a logical networking component in a VPC that represents a virtual network card.

21. What are the different uses of Internet gateway?

Internet gateway has two main utilizations:

• All the resources in a subnet are assigned with private IP and they don’t know their public IP. The network address translation for instances which have been assigned public IP
• Another use of an internet gateway is to make the resource in a subnet internet accessible. In other words, a subnet is made public with the help of an internet gateway.

22. Full form of NAT?

Network Address Translation.

23. What is a NAT instance?

Resources present in the private subnet can use NAT instances to access the internet. Though we still cannot access these instances from outside, hence keeping them secure.

24. How to set up a NAT instance?

We have to create a NAT instance using the already present AMI [Amazon machine images] in the public subnet. And route out the traffic from the private subnets route table to this particular instance.

25. What are different levels of security present in AWS to prevent your resources?

There are two security layers present for our resources in AWS VPC. One is network level security, also known as NACL (Network access control list) and another one is instance level security known as security group (SG).

26. What type of security is present at subnet level?

We can create a network access control list [NACL] to allow or block traffic from specific IP addresses.

27. What are different types of storage present in AWS?

• Block Based (EBS)
• File Based (EFS)
• Object Based (S3)

28. What is EBS?

Allows you to create storage volumes and attach them to EC2 instances. Notably we can think of it as a hard disk which we can attach to a VM. 

29. Why is there a need for EFS when there is S3 already present?

As S3 is object-based storage we cannot store files with locks and permissions. Therefore, it is not possible to mount a S3 to an EC2 instance. Whereas EFS is file-based storage and it can be used to mount to multiple EC2 instances.

30. What is an AMI?

AMI [Amazon machine Images] are pre-configured images which provide information to launch instances in the cloud. In fact, these are the backbone of the EC2 instances. Meanwhile we can create our own AMI as well with the software configured as per our need. We can share the same AMI with public or privately within the same region or different region.

31. What does an AMI consist of?

An AMI includes the following:

• A template for the root volume for the instance (for example, an operating system, an application server, and applications)
• Launch permissions that control which AWS accounts can use the AMI to launch instances
• A block device mapping that specifies the volumes to attach to the instance when it’s launched.

32. What is SDD, HDD and its difference?

• SDD - Solid State Drive – It stores the data in integrated circuits.

• HDD - Hard Disk Drive - stores data magnetically, through spinning disks.

33. What are different types of EBS volume types?

• SSD Based: SSD is flash based with no moving parts. All points in SSD are highly available and accessible which makes them very good candidate for good I/O performance.
• HDD based: HDD is made up of moving parts. Eventually these parts have to move to the data location to read it. And hence a bad candidate for I/O operations. But it has very good performance for sequential I/O.

34. How many buckets can a user create in AWS by default?

Users can create up to 100 buckets by default in each of the AWS accounts.

35. Differentiate between terminating and stopping an instance?

• Terminating an instance: Termination is in total contrast with stopping. Once you terminate your instance, all the instances connected to your EBS Volumes instance get deleted, no matter if you have saved them or not. This process can not be undone, and you can not access your instance again.
• Stopping an instance: When you stop an instance, it simply means that you are applying a temporary shutdown. EBS volumes still remain intact in the instances. Stopping does not result in any kind of data loss. It means that once you restart your instance, you can resume it from the point where it last left.

36. How many Elastic IPs can you create?

5 elastic IP addresses you can create per AWS account per region.

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