AWS Interview Questions – Set 01

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What are policies and what are the different types of policies?

Policy is an object which is associated with a resource that defines the permissions. AWS evaluate these policies when user makes a request. Permissions in the policy determine whether to allow or to deny an action. Policies are stored in the form of a JSON documents.

AWS supports six types of policies:

  • Identity-based policies
  • Resource-based policies
  • Permissions boundaries
  • Organizations SCPs
  • Access Control Lists
  • Session policies

Identity-based policies
Identity-based policies are the permissions stored in the form of JSON format. This policy can be attached to an identity user, group of users or role. It determines the actions that the users can perform, on which resources, and under what conditions.
Identity-based policies are further classified into two categories:
Managed Policies: Managed Policies are the identity-based policies which can be attached to multiple users, groups or roles. There are two types of managed policies:
AWS Managed Policies
AWS Managed Policies are the policies created and managed by AWS. If you are using the policies first time, then we recommend you to use AWS Managed Policies.
Custom Managed Policies
Custom Managed Policies are the identity-based policies created by user. It provides more precise control over the policies than AWS Managed Policies.
Inline Policies
Inline Policies are the policies created and managed by user. These policies are encapsulated directly into a single user, group or a role.
Resource-Based Policies
Resource-based policies are the policies which are attached to the resource such as S3 bucket. Resource-based policies define the actions that can be performed on the resource and under what condition, these policies can be applied.
Permissions boundaries
Permissions boundaries are the maximum permissions that identity-based policy can grant to the entity.
Service Control Policies (SCPs)
Service Control Policies are the policies defined in a JSON format that specify the maximum permissions for an organization. If you enable all the features in an Organization, then you can apply Service Control Policies to any or all of your AWS accounts. SCP can limit the permission on entities in member accounts as well as AWS root user account.
Access Control Lists (ACLs)
ACL defines the control that which principals in another AWS account can access the resource. ACLs cannot be used to control the access of a principal in a different AWS account. It is the only policy type which does not have the JSON policy document format.

Can you establish a peering connection to a VPC in a different region?

No, it’s not possible to establish a peering connection to a VPC in a different region. It’s only possible to establish a peering connection to a VPC in the same region.

What is Cross Region Replication?

Cross Region Replication is a service available in aws that enables to replicate the data from one bucket to another bucket which could be in a same or different region. It provides asynchronous copying of objects, i.e., objects are not copied immediately.

What is a Load Balancer?

Load Balancer is a virtual machine that balances your web application load that could be Http or Https traffic that you are getting in. It balances a load of multiple servers so that no web server gets overwhelmed.

How to connect EBS volume to multiple instances?

You cannot connect the EBS volume to multiple instances. But, you can connect multiple EBS volumes to a single instance.

What is Auto Scaling?

Auto Scaling is a feature in aws that automatically scales the capacity to maintain steady and predictable performance. While using auto scaling, you can scale multiple resources across multiple services in minutes. If you are already using Amazon EC2 Auto- scaling, then you can combine Amazon EC2 Auto-Scaling with the Auto-Scaling to scale additional resources for other AWS services.

Benefits of Auto Scaling

Setup Scaling Quickly
It sets the target utilization levels of multiple resources in a single interface. You can see the average utilization level of multiple resources in the same console, i.e., you do not have to move to the different console.
Make Smart Scaling Decisions
It makes the scaling plans that automate how different resources respond to the changes. It optimizes the availability and cost. It automatically creates the scaling policies and sets the targets based on your preference. It also monitors your application and automatically adds or removes the capacity based on the requirements.
Automatically maintain performance
Auto Scaling automatically optimize the application performance and availability even when the workloads are unpredictable. It continuously monitors your application to maintain the desired performance level. When demand rises, then Auto Scaling automatically scales the resources.

What is Redshift?

  • Redshift is a fast, powerful, scalable and fully managed data warehouse service in the cloud.
  • It provides ten times faster performance than other data warehouse by using machine learning, massively parallel query execution, and columnar storage on high-performance disk.
  • You can run petabytes of data in Redshift datawarehouse and exabytes of data in your data lake built on Amazon S3.

What are the components of AWS?

The following are the main components of AWS are:

Simple Storage Service: S3 is a service of aws that stores the files. It is object-based storage, i.e., you can store the images, word files, pdf files, etc. The size of the file that can be stored in S3 is from 0 Bytes to 5 TB. It is an unlimited storage medium, i.e., you can store the data as much you want. S3 contains a bucket which stores the files. A bucket is like a folder that stores the files. It is a universal namespace, i.e., name must be unique globally. Each bucket must have a unique name to generate the unique DNS address.
Elastic Compute Cloud: Elastic Compute Cloud is a web service that provides resizable compute capacity in the cloud. You can scale the compute capacity up and down as per the computing requirement changes. It changes the economics of computing by allowing you to pay only for the resources that you actually use.
Elastic Block Store: It provides a persistent block storage volume for use with EC2 instances in aws cloud. EBS volume is automatically replicated within its availability zone to prevent the component failure. It offers high durability, availability, and low-latency performance required to run your workloads.
CloudWatch: It is a service which is used to monitor all the AWS resources and applications that you run in real time. It collects and tracks the metrics that measure your resources and applications.
Identity Access Management: It is a service of aws used to manage users and their level of access to the aws management console. It is used to set users, permissions, and roles. It allows you to grant permission to the different parts of the aws platform.
Simple Email Service: Amazon Simple Email Service is a cloud-based email sending service that helps digital marketers and application developers to send marketing, notification, and transactional emails. This service is very reliable and cost-effective for the businesses of all the sizes that want to keep in touch with the customers.
Route53: It is a highly available and scalable DNS (Domain Name Service) service. It provides a reliable and cost-effective way for the developers and businesses to route end users to internet applications by translating domain names into numeric IP addresses.

What are different types of instances?

Following are the different types of instances:

General Purpose Instance type
General purpose instances are the instances mainly used by the companies. There are two types of General Purpose instances: Fixed performance (eg. M3 and M4) and Burstable performance (eg. T2). Some of the sectors use this instance such as Development environments, build servers, code repositories, low traffic websites and web applications, micro-services, etc.

Following are the General Purpose Instances:
T2 instances: T2 instances are the instances that receive CPU credits when they are sitting idle and they use the CPU credits when they are active. These instances do not use the CPU very consistently, but it has the ability to burst to a higher level when required by the workload.
M4 instances: M4 instances are the latest version of General purpose instances. These instances are the best choice for managing memory and network resources. They are mainly used for the applications where demand for the micro-servers is high.
M3 instances: M3 instance is a prior version of M4. M4 instance is mainly used for data processing tasks which require additional memory, caching fleets, running backend servers for SAP and other enterprise applications.
Compute Optimized Instance type
Compute Optimized Instance type consists of two instance types: C4 and C3.
C3 instance: C3 instances are mainly used for those applications which require very high CPU usage. These instances are mainly recommended for those applications that require high computing power as these instances offer high performing processors.
C4 instance: C4 instance is the next version of C3 instance. C4 instance is mainly used for those applications that require high computing power. It consists of Intel E5-2666 v3 processor and use Hardware virtualization. According to the AWS specifications, C4 instances can run at a speed of 2.9 GHz, and can reach to a clock speed of 3.5 GHz.
GPU Instances
GPU instances consist of G2 instances which are mainly used for gaming applications that require heavy graphics and 3D application data streaming. It consists of a high-performance NVIDIA GPU which is suitable for audio, video, 3D imaging, and graphics streaming kinds of applications. To run the GPU instances, NVIDIA drivers must be installed.
Memory Optimized Instances
Memory Optimized Instances consists of R3 instances which are designed for memory- intensive applications. R3 instance consists of latest Intel Xeon lvy Bridge processor. R3 instance can sustain a memory bandwidth of 63000 MB/sec. R3 instance offers a high- performance databases, In memory analytics, and distributed memory caches.
Storage Optimized Instances
Storage Optimized Instances consist of two types of instances: I2 and D2 instances.
I2 instance: It provides heavy SSD which is required for the sequential read, and write access to a large data sets. It also provides random I/O operations to your applications. It is best suited for the applications such as high-frequency online transaction processing systems, relational databases, NoSQL databases, Cache for in-memory databases, Data warehousing applications and Low latency Ad- Tech serving applications.
D2 instance: D2 instance is a dense storage instance which consists of a high-frequency Intel Xeon E5-2676v3 processors, HDD storage, High disk throughput.

How many subnets can you have per VPC?

You can have 200 subnets per VPC.