Common AWS Interview Questions for 2023 - IQCode

AWS Cloud Computing Services: EC2

Amazon Web Services (AWS) is a cloud computing service provided by Amazon that allows users to develop, test, deploy, and manage applications and services. AWS accomplishes this by utilizing Amazon's data centers and hardware. AWS offers Infrastructure-as-a-Service (IaaS), Platform-as-a-Service (PaaS), and Software-as-a-Service (SaaS) services.

One of the services provided by AWS is EC2 - Elastic Compute Cloud. EC2 enables users to create virtual machines equipped with processing power, storage capacity, analytics, networking, and device management capabilities. AWS uses a pay-as-you-go pricing model, which eliminates the need for upfront costs and allows you to pay monthly based on usage.

Below is a list of popular AWS interview questions and answers:

AWS Basic Interview Questions:

1. What is EC2?

Overview of CloudWatch

CloudWatch is a monitoring and logging service provided by Amazon Web Services (AWS). Its main purpose is to help users track and analyze the operational performance and usage of their AWS resources and applications. CloudWatch provides the ability to collect and monitor metrics, log files, and alarms for AWS resources in real-time. This allows users to gain valuable insights into their infrastructure and respond quickly to issues before they become critical. Additionally, CloudWatch provides a range of analysis tools to help users troubleshoot issues and optimize resource utilization. Overall, CloudWatch is an essential tool for AWS users looking to maintain a high level of visibility and control over their cloud infrastructure.

What is Elastic Transcoder?

Elastic Transcoder is a cloud-based media transcoding service provided by Amazon Web Services (AWS). It allows users to convert audio and video files into multiple formats that are optimized for different devices and playback scenarios. The service is highly scalable and can handle large volumes of media at once. It is commonly used by businesses and developers to streamline their media workflows and deliver high-quality content to their users.

Understanding VPC

VPC stands for Virtual Private Cloud and is a service provided by Amazon Web Services (AWS) that allows users to create a virtual network in the cloud. It is essentially a customizable virtual data center that enables users to launch AWS resources within a defined virtual network. Users can configure IP addresses, subnets, route tables, and network gateways to create the desired network topology. With VPC, users can also control network security using security groups and network ACLs to restrict access to resources.

DNS and Load Balancer Services under which type of Cloud Service?

DNS and Load Balancer services fall under the category of Infrastructure as a Service (IaaS) in cloud computing.

Amazon S3 Storage Classes

In Amazon S3, there are various storage classes available to meet different performance, durability, and cost requirements. These storage classes include:


: It offers high durability and availability and is most suitable for frequently accessed data.

STANDARD_IA (Infrequent Access)

: This class is for data that is accessed less frequently, but when required, needs rapid access.


: This storage class is designed for data with unknown or changing access patterns, and it automatically moves data to the most cost-effective tier.


: It provides secure, durable, and low-cost data archiving. Data retrieval times range from minutes to hours.


: This storage class is for data that can be accessed once or twice a year and has retrieval times ranging from 12 to 48 hours. It is essential to choose the right storage class for your data to ensure optimal performance and cost-effectiveness.

T2 Instances: Overview

T2 instances are a type of Amazon Elastic Compute Cloud (EC2) instance that provides a balance of compute, memory, and network resources for a broad range of general-purpose workloads. T2 instances are designed to provide a low-cost option for workloads that don't use the full CPU often, but occasionally need bursts of CPU power.

T2 instances use credits to accumulate CPU resources. The instances can burst above their baseline level when they have accumulated sufficient credits. Once the accumulated credits are depleted, the CPU performance returns to the baseline level.

In summary, T2 instances provide a cost-effective and flexible option for workloads that don't have a consistently high demand for CPU resources.

Explanation of Key Pairs in AWS

In Amazon Web Services (AWS), key pairs refer to an access credential that is used to authenticate users attempting to access an EC2 instance securely. The key pair consists of a public key, which is stored on the instance, and a private key, which is retained by the user.

When an EC2 instance is launched, its security group rules are configured to allow specific inbound traffic. The instance is secured by using key pairs, which are necessary to log in to the instance. A user may also associate a specific key pair with an instance when creating or launching the instance.

This method of authentication is more secure than relying solely on a password since only the user with the matching private key can access the instance. It is recommended that users store their private keys securely and never share them with anyone.

Maximum Subnets per VPC

In Amazon Web Services (AWS), the maximum number of subnets allowed per Virtual Private Cloud (VPC) depends on the IP address range of the VPC. Each subnet must reside within a unique availability zone (AZ) and may not overlap with other subnets. Generally, it is recommended to limit the number of subnets per VPC to fewer than 200. However, technically, the maximum number of subnets per VPC can be calculated using the following formula:

Maximum number of subnets = 2^(32 - # of bits in VPC IP address range) - 5

For example, if an organization uses a VPC with an IP address range of, then the maximum number of subnets that can be created within that VPC is 2^(32-16) - 5 = 65,531.

List of Different Types of Cloud Services

Cloud computing is a widely used technology in modern-day IT infrastructure. It provides data storage, processing, and management services over the internet. Here are some of the commonly used cloud services:

- Infrastructure as a Service (IaaS) - Platform as a Service (PaaS) - Software as a Service (SaaS) - Database as a Service (DBaaS) - Backend as a Service (BaaS) - Function as a Service (FaaS) - Mobile Backend as a Service (MBaaS) - Disaster Recovery as a Service (DRaaS) - Desktop as a Service (DaaS)

Each cloud service has its own set of features and benefits. It is important for businesses to choose the right cloud service based on their specific needs to achieve maximum efficiency and better results.

Explanation of Amazon S3

Amazon S3 (Simple Storage Service) is a cloud-based data storage service provided by Amazon Web Services (AWS). It is a scalable, secure, and cost-effective solution for storing and retrieving any type of data. S3 is designed to provide 99.999999999% durability and 99.99% availability of objects over a given year. It is ideal for a wide variety of use cases, including backup and archiving, content storage and distribution, data lakes, big data analytics, and mobile, web, and IoT applications.

Using S3, you can upload any amount of data and access it from anywhere in the world, using a simple web interface, a RESTful API, or SDKs for popular programming languages such as Java, Python, and Ruby. You can also use S3 to host static websites, distribute media files, and share data with other AWS services, such as EC2, Lambda, and Redshift.

S3 provides several features to help you manage your data, such as bucket policies, object lifecycle rules, versioning, server access logging, and encryption. You can also use S3 with other AWS services, such as Amazon CloudFront, Amazon Glacier, AWS Snowball, and AWS Storage Gateway, to create a complete storage solution for your applications.

How Amazon Route 53 Achieves High Availability and Low Latency

Amazon Route 53 achieves high availability and low latency by using a global network of DNS servers that are geographically distributed around the world. When a user types a domain name in their browser, the request is routed to the nearest DNS server, which then returns the IP address of the server hosting the website.

Route 53 also uses health checks to monitor the status of servers hosting websites. If a server fails its health check, Route 53 automatically redirects traffic to a healthy server to maintain availability.

Additionally, Route 53 offers features such as traffic routing policies, which allow users to control how traffic is distributed between different resources, and DNS failover, which automatically redirects traffic to a backup resource in case of an outage.

Overall, these measures ensure that Route 53 provides reliable and fast DNS services to customers, helping to ensure flawless performance of their web applications and services.

Sending a Request to Amazon S3

To send a request to Amazon S3, you can use the APIs provided by Amazon S3. These APIs are offered in different programming languages such as Java, Python, Ruby, etc. The requests can be sent using HTTP methods like GET, PUT, POST, DELETE, etc.

Below is an example of sending a GET request to Amazon S3 to retrieve the contents of an object:

import boto3

s3 = boto3.client('s3') response = s3.get_object(Bucket='your_bucket_name', Key='your_object_key')


In this example, we are using the Python SDK for Amazon S3. The client is created using the 'boto3' module, and then we are calling the 'get_object' method on the client to retrieve the contents of the object specified by its keyname. The response contains the object data and other metadata that can be used for further processing.

What is included in AMI?

AMI (Amazon Machine Image) includes the information required to launch an instance, which includes:

  • The operating system
  • The application server
  • Other software required for the machine to run
  • Launch permissions that control which AWS accounts can use the AMI to launch instances
Tip: AMIs are customized and shared across multiple users allowing them to create an instance with the software that fits their specific needs.

Types of Instances

There are several types of instances in programming, including:

  • Class instances: objects created from a class
  • Module instances: objects created from a module
  • Function instances: objects created from a function
  • Built-in instances: objects created from built-in types like list, dictionary, etc.
  • User-defined instances: objects created from classes created by the user

Each instance has its own set of data and behavior, determined by the class or type it was created from.

Understanding the Relationship between Availability Zone and Region

In cloud computing, a region refers to a specific geographic location where a cloud provider's data centers are located. An availability zone, on the other hand, is a specific data center within a region that operates independently of other data centers within the same region.

An availability zone is designed to be physically and logically separate from other availability zones in the same region. This ensures that applications are highly available and fault-tolerant. For example, if a user is running an application in one availability zone and that zone experiences an outage, the application can automatically failover to another availability zone within the same region, which ensures service continuity.

Therefore, multiple availability zones within a region provide redundancy, fault tolerance, and disaster recovery capabilities. They also enable users to deploy and run applications in a highly available and scalable manner.

Monitoring Amazon VPC

To monitor Amazon VPC, you can use Amazon CloudWatch, which is a monitoring service provided by Amazon Web Services. Here are the steps to monitor Amazon VPC:

1. Go to the AWS Management Console and open the CloudWatch console.

2. In the left-hand menu, select "Logs" and then select "Log groups".

3. Choose the log group for your VPC, and then select "Create Metric Filter".

4. Set up the metric filter to capture the desired log data.

5. Once the metric filter has been set up, it should start sending data to Amazon CloudWatch and you can view the metrics in the CloudWatch Metrics console.

6. You can also set up CloudWatch Alarms to notify you when metrics meet certain thresholds or conditions.

By monitoring Amazon VPC with CloudWatch, you can keep track of network traffic, latency, and other important metrics in real time, helping you to maintain optimal network performance.

Types of Amazon EC2 Instances According to their Costs

Amazon Elastic Compute Cloud (EC2) offers a variety of instances with different costs to meet various workloads and use cases. Some of the types of EC2 instances based on their costs include:

1. On-demand instances - These instances allow you to pay for what you use without any upfront payment or long-term commitment. 2. Reserved instances - These instances require an upfront payment to reserve capacity for a specified period, which can help save up to 75% compared to on-demand prices. 3. Spot instances - These instances let you bid on unused EC2 capacity, which can significantly reduce the instance cost; however, spot instances can be terminated at any time with two minutes of notification. 4. Dedicated hosts - These instances give you complete control over EC2 instance placement on a physical server and can help you reduce licensing costs by using your existing server-bound software licenses.

Overall, choosing the right EC2 instance type and cost largely depends on your specific workload requirements, budget, and utilization patterns. By evaluating these factors, you can optimize the cost and performance of your EC2 instances.

Stopping and Terminating an EC2 Instance

When you stop an EC2 instance, the instance is put in a **stopped state**. This means that the instance's Amazon EBS volumes are still available and that you are not charged for hourly instance usage while it is stopped. You can start the instance again at any time.

However, when you terminate an EC2 instance, the instance and its associated Amazon EBS volumes are **completely deleted**. This means that you cannot start the instance again and that you lose any data stored on its EBS volumes. Therefore, it is important to be very careful when deciding whether to stop or terminate an EC2 instance.

The Consistency Models Offered by AWS for Modern Databases

AWS offers different consistency models for modern databases, including:

- Strong Consistency: This model ensures that all data reads return the most up-to-date version of the data, guaranteeing consistency across all copies of the database.

- Eventual Consistency: This model allows for data updates to propagate across multiple copies of the database, but doesn't guarantee immediate consistency across all copies. However, eventual consistency models are often more cost-effective and performant.

- Read After Write Consistency: This model ensures that any data written to the database is immediately available for subsequent reads.

- Session Consistency: This model ensures that all reads and writes made within a session receive consistent results.

It's important to choose the right consistency model based on the requirements of your application and the trade-offs between consistency and performance.

Understanding Geo-Targeting in CloudFront

Geo-Targeting in CloudFront is a feature that allows content distributors to serve different content to their audience based on their geographic location. Essentially, it helps in delivering region-specific content and enhances the overall user experience.

To implement Geo-Targeting in CloudFront, an Amazon CloudFront distribution needs to be created with the appropriate settings. The feature leverages the geographical information of viewers, which is retrieved by examining the IP address of the viewer's request. This information is then matched with the geo-mapping rules that are defined in the CloudFront web distribution.

Overall, Geo-Targeting in CloudFront is a powerful tool that can be used to enhance the overall user experience and provide tailored content to specific regions.

Advantages of AWS IAM

AWS IAM (Identity and Access Management) offers several advantages, including:

1. Enhanced Security: IAM provides centralized control over the management of AWS resources, ensuring that only authorized personnel can access them.

2. Granular Access Control: IAM allows fine-grained control over user permissions to AWS resources, enabling administrators to easily manage access to specific AWS services.

3. Easy Integration: IAM can be easily integrated with other AWS services, such as Amazon EC2 and Amazon S3, to provide secure access to resources.

4. Flexible Policies: IAM offers flexible policies that can be used to define permissions at the user, group, or role level.

5. Compliance: IAM helps to meet compliance requirements by providing detailed logs and access reports, which can be used for auditing and compliance purposes.

6. Cost-Effective: IAM is a cost-effective solution that enables organizations to manage access to their AWS resources without having to invest in additional hardware or software.

Overall, AWS IAM provides a simple, secure, and cost-effective way to manage access to AWS resources.

Understanding Security Groups

In the context of computer networking, a security group is a virtual firewall that controls the incoming and outgoing traffic of a particular network. It acts as a filter to determine which traffic is allowed and which traffic is blocked. Security groups can be used to restrict access to resources, limit exposure to potential security threats, and enforce security policies within an organization. They are commonly used in cloud computing environments such as Amazon Web Services (AWS) to secure instances and resources.

Explanation of Spot Instances and On-Demand Instances

In Amazon Web Services (AWS), Spot Instances refer to the type of instances that an individual can bid on and use at a much lower cost than on-demand instances. The downside to this is that Spot Instances can be taken back by AWS if someone bids higher than you, which would cause the instance to terminate.

On the other hand, On-Demand Instances are instances that are available to the user at a fixed-rate, which is usually predetermined by AWS. These instances are a bit more expensive but do not have the same risk of being taken back as with Spot Instances.

Both Spot Instances and On-Demand Instances have their own advantages and disadvantages. However, depending on the use case, one may be more beneficial than the other.

Explanation of Connection Draining

Connection Draining is a procedure followed by load balancers to cease the flow of traffic to a particular server instance before it gets terminated. This process ensures that any ongoing requests are completed before closing the server instance. This technique helps to minimize the disruption of services during server updates or maintenance. In simple terms, Connection Draining is like waiting for people to exit a building before shutting it down.

Stateful and Stateless Firewalls Explained

Stateful firewalls are firewalls that keep track of the state of network connections. They monitor the whole connection between two systems and keep track of the state of the connection, such as the sequence numbers used and the status of the connection. This information is then used to determine if a packet is allowed to pass through the firewall or not.

Stateless firewalls, on the other hand, do not keep track of the state of network connections. They filter packets based on the content of the packet itself, such as the source and destination IP address, port numbers, and protocol type. They do not take into account the state of the connection.

Understanding Power User Access in AWS

Power User Access is a built-in policy on Amazon Web Services (AWS) that provides a certain level of access to AWS services and resources. This access level reflects a balance between full administrator access and read-only access.

Power Users cannot create or delete policies, users, or access keys, but they can perform activities that would otherwise require full administrative access. A Power User can use the Access Policy option to change access policies for the user groups to which they belong.

Generally, Power Users are employees who require access to AWS services and resources to perform their day-to-day business activities but do not require the full administrator access. The access level grants permissions to read all the resources in various services whereas creating or modifying the resources is not allowed.

A Power User has the capability to access key services, such as EC2 instances, S3 buckets, and RDS DB instances among others. They can also create snapshots from EBS volumes in their own zones and migrate the volumes between zones.

Overall, Power User Access provides users with the necessary access to AWS resources with a level of security to prevent destruction or disruption of production applications.

Instance Store Volume vs EBS Volume

In Amazon Web Services, an Instance Store Volume is a temporary storage volume that is physically attached to the EC2 instance. It provides high I/O performance and is ideal for temporary data that is frequently accessed.

On the other hand, an EBS (Elastic Block Store) Volume is a persistent storage device that you can attach and detach from your EC2 instance. It is ideal for storing data that requires frequent and consistent access, and provides reliability, durability, and scalability. EBS Volumes can also be backed up and restored as needed.

Understanding Recovery Time Objective (RTO) and Recovery Point Objective (RPO) in AWS

In AWS, Recovery Time Objective (RTO) and Recovery Point Objective (RPO) are two crucial parameters for disaster recovery planning.

RTO is the maximum time duration within which the system or application must be restored after a disaster, in order to avoid adverse effects on business operations. RPO, on the other hand, refers to the maximum amount of data that a company can afford to lose without causing significant harm or data loss.

It is important to note that RTO and RPO should be determined based on the business's needs and priorities. AWS provides various tools and services, such as AWS Backup and AWS Disaster Recovery, to help businesses meet their recovery objectives and ensure business continuity in the event of a disaster.

Uploading Files Larger Than 100 MB to Amazon S3

Yes, it is possible to upload a file larger than 100 megabytes to Amazon S3. However, you will need to use Amazon's multipart upload API, which allows you to upload files in parts. This API splits the large file into smaller parts and uploads them in parallel, which can make the upload process faster and more efficient.

To use the multipart upload API, you can use an SDK or a REST API provided by AWS. With the SDK, you can use the appropriate programming language, such as Java, Python, or .NET, to upload the large file. With the REST API, you can use HTTP methods, such as PUT or POST, to initiate the upload and upload each part.

Keep in mind that when using the multipart upload API, you will need to manage the parts and track their upload progress. Also, Amazon S3 charges per request and storage, so be aware of the costs associated with uploading and storing large files.

Changing the Private IP Address of an EC2 Instance

In AWS, is it possible to modify the private IP address of an EC2 instance while it is running or in a stopped state?

plain text:

It is not possible to change the private IP address of an EC2 instance while it is running. However, you can change the private IP address of a stopped instance by releasing its current private IP address and assigning a new one when you restart the instance. Alternatively, you can create a new network interface with the desired IP address and attach it to the instance.

Understanding the Usage of Lifecycle Hooks in Autoscaling

In autoscaling, lifecycle hooks allow the administrator to control how instances are launched or terminated. These hooks enable the execution of customized scripts/assets in response to certain events in the lifecycle of an instance, such as launching or terminating an instance in the autoscaling group.

When an instance is launched or terminated, lifecycle hooks accept parameters, such as a Lambda function or an SNS topic, that can perform pre-configured actions such as disabling alarms, updating dashboards, removing items from queues, etc. Additionally, these hooks allow inspection and validation of instances to ensure that they meet the required conditions before they are launched.

By using lifecycle hooks, administrators can ensure their instances run more efficiently, reduce downtimes, and improve their overall application or system performance.

What Policies can be Set for User Passwords?

In order to ensure the security of user accounts, various policies can be set for passwords. These policies may include:

  • Minimum length of the password
  • Requirement of special characters, uppercase and lowercase letters, and/or numbers
  • Maximum age of password
  • Enforcement of password history to prevent repetition of previous passwords
  • Lockout after multiple failed login attempts
  • Two-factor authentication to add an extra layer of security

By implementing these policies, you can minimize the risk of unauthorized access and ensure the safety of user data.

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