100 most important AWS interview questions and answers for 2025

Currently, the three basic types of cloud computing include the following:

• Infrastructure as a Service (IaaS)
• Platform as a Service (PaaS)
• Software as a Service (SaaS)

The similarity between Availability Zones and Regions is that they both provide geographical redundancy and isolation for cloud infrastructure in the AWS cloud. Availability Zones are distinct locations within a given Region, while Regions are geographic areas with multiple Availability Zones.

Auto-scaling is a cloud computing feature that allows a system to automatically scale its resources up or down based on demand or predetermined conditions. This is typically used to ensure that there are enough resources to handle the load on a system, while also avoiding over-provisioning and keeping costs low.

AWS CloudFormation Solution helps you easily manage AWS resources. The steps are mentioned below:

• Create and use an existing CloudFormation template with the help of YAML or JSON format
• The code then needs to be stored in an S3 bucket.
• Call the bucket using AWS CloudFormation and on your template you need to create a stack
• CloudFormation reads the files, their order, and the relationship between the services, provisions the services one after the other, and understands the services that are called.

This is one of the most common AWS basic interview questions. However, to answer this well, you must list down all the required steps for the procedure. Listed below are the steps to be followed to upgrade or downgrade a system ensuring near-zero downtime:

• Open EC2 console
• Select Operating System AMI
• Initiate an instance with the new instance type.
• Install updates
• Install applications
• Test the instance
• If working, deploy to the new instance and replace the previous instance.Soon, it's deployed, and now you can upgrade or downgrade

Following are four examples of AWS services that are not region-specific:

• Route 53: A domain name system service
• IAM: Helps access AWS resources securely
• Web Application Firewall: To separate web-application and the internet
• Cloudfront: A content delivery network to deliver app, videos or data from providers to consumers quickly.

The Bandwidth of NAT Gateway is up to 45 Gbps and can automatically scale based on traffic requirements whereas, in NAT Instance, it depends on instance bandwidth.

Elastic Transcoder is an AWS service tool that supports multiple devices with various resolutions and formats of video, like laptops, tablets, and smartphones. It is a cloud-based media transcoding service provided by Amazon Web Services (AWS) that enables you to convert video and audio files from one format to another. The service supports a wide range of input and output formats, codecs, and resolutions, making it easier to deliver content to various devices, including laptops, tablets, and smartphones.

EC2 is also called Elastic Compute Cloud. Amazon EC2 is used to launch virtual computing servers as needed, manage storage, and configure security and networking.

Amazon EC2 offers restricted access, allowing only trusted networks to access ports on an instance. In addition, Amazon EC2 allows you to access only those permissions you require and disable other password-based logins for instances launched from your AMI.

Some best practices are as follows:

• Using identity federation to manage AWS resources and APIs
• Using least permissive rules
• Using Amazon inspector to check any software vulnerabilities

Yes, Amazon S3 can be used with Amazon EC2. Here, Amazon S3 gives developers access to a highly reliable, fast and scalable data storage infrastructure.

AWS provides the following tools to get reliable data for making cost forecasts, optimizations, or for managing the costs.

• AWS Cost Explorer: Helps to track costs incurred and data used over time.
• AWS Budgets: Helps set custom spending plan on aws for specific time.
• Cost Allocation Tags: Provides tags that can be assigned to resources within your AWS account so that you can track usage and cost of AWs resources.

T2 instances are low-cost instance types for general use. They provide base-level CPU performance but can provide bursts above the baseline. They work best where full CPU capacity is not needed constantly and is only needed to burst higher CPU performance.

There are various tools that can log into the cloud environment, in addition to the console. Some common ones include:

• Putty
• AWS CLI for Linux
• AWS CLI for Windows
• Eclipse
• AWS SDK

A centralized logging solution enables organizations to gather, analyze and display Amazon CloudWatch Logs in one central place. You can use Amazon CloudWatch Logs, Amazon ElasticSearch, and Amazon Kinesis to create a centralized logging solution.

Two popular AWS services that provide security log data to provide insight into how the service is operating are:

• AWS CloudTrail
• AWS Config

Besides this, AWS Security Hub and AWS GuardDuty can also be used for insights into your security.

DDoS is a cyber-attack. Here, the perpetrator accesses a website and creates numerous sessions so that the other fair users cannot access the service.

The following tools can be used to minimize DDoS attacks on AWS services:

• AWS Shield
• AWS Waf
• Amazon CloudFront
• ELB
• Virtual Private Cloud (VPC)

Using Amazon CloudWatch, you can set up a system monitor to monitor state changes in scheduled events, Amazon EC2, Auto-scaling lifecycle events, AWS API calls
and Console sign-in events.

Beside this, you can also use AWS Lambda and AWS Elasticsearch for real-time website metrics monitoring.

There are three types of virtualization in AWS. These include:

• Hardware Virtual Machine (HVM)
• Paravirtualization (PV)
• Paravirtualization on HVM

Stopping an EC2 instance means you are normally shutting it down and moving it to a stopped state. On the other hand, terminating the instance means you are permanently deleting the instance. When this happens, it’s attached volumes are deleted and you cannot recover them.

The three types of EC2 instances based on their costs are as follows:

• On-demand Instance
• Spot Instance
• Reserved Instance

SSH agent forwarding is a process whereby a SSH server gets access to SSH client and can be enabled as follows:

Enable SSH agent

#starting up ssh-agent in the background
$ eval "$(ssh-agent -s)"
Agent pid 6969

Now, we add SSH key to the SSH-agent

$ ssh-add ~/.ssh/id_rsa

Connect to the host

ssh -i ~/.ssh/id_rsa user@our_host_ip

No, both operating systems are not available with Amazon Web Service.

You can follow these steps to set the AWS CloudWatch to recover an EC2 instance:

• Create an Alarm using Amazon CloudWatch
• Then, Define Alarm→ Actions tab
• Choose to Recover this

The three most common types of AMI designs are as follows:

• Fully Baked AMI
• Just Enough Baked AMI (JeOS AMI)
• Hybrid AMI

Key-pairs in AWS are secured login information for virtual machines. They are password protected login credentials to verify your identity while connecting the Amazon EC2 instances. AWS key-pairs are made up of private and public keys that connect to the instances.

S3 stands for Simple Storage Service. Amazon S3 is the best-supported storage platform available. It helps to supervise data for cost optimization, compliance, and access control.

The following steps can be followed to recover an EC2 instance whose key has been lost:

• Check that the EC2Config service is running
• Stop the original instance before proceeding further
• Separate the root volume for the instance
• Attach it to a temporary instance
• Mount the volume on temporary instance
• Modify the configuration file
• Unmount the volume and detach it from temporary instance
• Reattach the volume to original instance
• Restart the original instance

Some of the policies that can be set for a user’s passwords, include:

• Minimum length of the password
• Particular character types
• Automatic expiration of password.

AWS S3 and EBS have different performance characteristics and are optimized for different use cases.

AWS S3 is designed for large-scale, durable, and cost-effective storage of unstructured data objects, and it provides a high level of scalability, availability, and durability.

AWS EBS, on the other hand, is a block-level storage service that provides persistent storage for EC2 instances. EBS volumes are optimized for low-latency, high-throughput workloads that require fast and reliable access to data, such as database servers, transactional processing systems, and high-performance computing applications.

You have to enable the DNS hostname resolution. By this, the problem itself resolves.

Three security products and features of AWS include:

• Security groups
• Network access control lists
• Flow logs

The security product features VPC offers include the following:

• Security groups act as a firewall for the EC2 instances and control traffic.
• Network access control acts as a firewall for the subnets and controls traffic.
• Flow logs capture the traffic from the network interfaces in your Virtual Private Cloud.

The Amazon VPC can be monitored using these tools:

CloudWatch: CloudWatch is a monitoring service from Amazon Web Services (AWS) that monitors network traffic, memory use and other aspects of your VPC.

VPC Flows Logs: A VPC Flows Log allows you to gather information about traffic movement in and out of VPC.

Two hundred subnets can be created in a single Amazon VPC.

We prefer Provisioned IOPS over Standard Rds Storage because it delivers high IO rates. Usually, we use Provisioned IOPS when there are batch-oriented workloads. However, it is expensive as compared to Standard Rds Storage.

Amazon Rds manages upgrading, patching, and data backups automatically. DynamoDB is used to deal with unstructured data. On the other hand, Redshift is used in data analysis.

AWS cloud supports many popular disaster recovery architectures. In addition, it provides a set of cloud-based disaster recovery services which enable rapid recovery of a business’s IT infrastructure and data. One major benefit it provides to businesses is system security, where it integrates backup, restoration and data protection into a disaster recovery plan, reducing security risks altogether.

A user can access to a particular bucket in AWS using any of the following methods:

• Create a bucket
• Create an IAM user or use an existing one
• Create an IAM policy
• Attach the policy to the IAM user:
• Test the user's access

Snowball provides secure, robust, and well-built devices enabling users to bring AWS computing and storage ability to an edge environment. Also, it helps in the transfer of data outside as well as inside of the AWS environment. These devices are known as AWS Snowball devices or AWS Snowball Edge devices.

You can follow these steps to transfer data through Snowball:

• Create a job
• Connect the application to the job
• Copy the data into the Snowball application
• Transfer the data to the AWS S3.

Some of the storage classes available in Amazon S3 include:

• S3 Outposts storage class
• Amazon S3 Standard-Infrequent Access
• Amazon S3 Standard
• Amazon S3 Intelligent-Tiering
• Amazon S3 Reduced Redundancy Storage

Amazon VPC is a way by which you can easily connect your own data center with your cloud resources. This means you can launch AWS resources in your pre-defined virtual network. With Amazon VPC, you can launch AWS resources such as EC2 instances, Elastic Load Balancers (ELBs) as well as RDS databases within your own defined virtual network.

Yes, we can create an Auto Scaling group in AWS by adding an existing instance using the following steps:

• Open EC2 console
• Select your instance under the instance
• Choose Action -> Instance Setting -> Attach to Auto Scaling Group
• Select a new Auto Scaling group
• Attach this group to the instance
• Edit the instance if needed
• After completing, you can successfully add the instance

Operational Costs such as cost of infrastructure

• Workforce Productivity: How much output you are able to obtain in a given time
• Cost Avoidance: Ensuring that the work is done in minimal time and with minimal cost
• Operational resilience:Ability to sustain operations in adverse circumstances.
• Business agility :Ability to rapidly respond to market changes.

RTO stands for Recovery Time Objective. The RTO is used to determine how quickly an organization’s application can recover after an outage occurs.

RPO stands for Recovery Point Objective. This indicates the maximum amount of data your application can tolerate losing due to an outage.

Where AWS CloudFormation helps you describe infrastructure resources that are present in your cloud environment, AWS Elastic Beanstalk provides an environment that eases the deployment and running of applications in the cloud.

Following are the elements that can be found in an AWS CloudFormation template:

• Template parameters
• Data tables
• Output values
• Resources and their configuration values
• File format version number

If one of the resources in a stack isn’t created successfully, the CloudFormation automatically rolls back and ends the resources created in the CloudFormation template.

Snowmobile is an exabyte-scale migration service that allows you to transfer large volumes of data up to 100 PB. Some of its use cases include:

• Migrating large amount of data
• Customizing data transfer operations for your locations.
• Keeping your data transfer secure.

AWS IAM assigns roles to multiple users and groups to create roles with defined access levels using IAM. Here are a few other key benefits of using AWS IAM:

• Better customer and user experience.
• Improved safety and risk management
• A greater control over users and data
• Reduced business costs.

Connection draining is the allowing of serving current requests on the servers. These requests can be either decommissioned or updated.

Power-users have owner access like an administrator user but can't control other users and permissions. The Power user access in AWS IAM gives permission to do other roles except using IAM. A user with this permission can create, view or remove resources from AWS accounts but can’t create other user's or alter any user’s permissions.

An EC2 backup using EBS can be automated through the following steps:

• Through API, listi instances and connect them to AWS
• Identify Volumes: Once you have identified the instances, the next step would be to identify the EBS volumes that are attached to them. This can be done using the ‘describe-volumes’ command.
• Then listing the snapshots for each volume and assigning a retention period too.
• Also, removing the snapshot older than the retention period.

EBS is a permanent storage where you can recover data at a later point from the storage. When you save data here, its stays even after EC2 instance lifetime. Whereas, EC2 on is a temporary storage, and hence, doesn’t allow data recovery.

Yes, it is possible to take a backup of EFS like EBS. Amazon EFS (Elastic File System) provides the ability to take point-in-time backups of your file system using Amazon EFS backup. With Amazon EFS backup, you can create a snapshot of your file system at a particular point in time and store it in AWS S3. You can then use the snapshot to restore your file system in the event of data loss or accidental deletion.

Here are the steps to follow:

• Sign in to your AWS console
• Click EFS-to-EFS-restore button
• Select region through region selector bar
• Check if you have selected the right template
• Put a name for your solution stack.
• Finally review the parameters for the template.

There are three types of load balancers in AWS. These include:

• Application Load Balancer: This is a layer 7 load balancer and routes traffic to targets such as EC2 instances.
• Network Load Balancer: This improves application availability and responsivity and prevents server overload.
• Classic Load Balancer : This operates at both the connection level and request level and provides load balancing across multiple Amazon EC2 instances.

Listed below are the uses for the load balancers in AWS Elastic Load Balancing:

• Application Load Balancer for flexible load management: It can detect if any server is not performing and automatically switches to another causing no downtime.
• Network Load Balancer for extreme performance: Can handle volatile work loads, handle millions of request per second and ofer support for containerized applications to list a few.
• Classic Load Balancer for EC2 Classic network: Distributes incoming traffic across multiple targets.

AWS IAM is a web service that securely controls access to AWS services. It provides a centralized view of resources that are allowed inside AWS and what permissions they have. It ensures that the right people and job roles in the organization can access the tools to do their jobs. It allows the organization to manage a range of identities whether it is people, software, or hardware like robotics and IoT devices. Basically an organization needs IAM to increase employee productivity and to provide online security.

AWS Web Application Firewall protects your web applications from any web exploitations and bots that can affect availability, security and consume excessive resources. It filters web traffic and prevents account takeover fraud. It creates and maintains rules by itself and incorporates them into the design and development process.

The following AWS IAM categories are the ones a user can control:

• Creating and managing IAM users and IAM groups
• Taking care of the security credentials of the users
• Policy management
• Access Management
• Identity Governance and Administration

Where the IAM role defines a set of permissions for AWS service requests, the IAM user has specific long-term credentials and you can assign IAM role to a user.

Two kinds of policies provided by AWS IAM are managed by the user and managed by AWS. These are built-in managed policies that can be attached to Roles or Users.In the case of the latter, the user is not able to change the configuration or policy as it is managed by AWS.

By managing IAM users and their access, you can centrally manage permissions that control which AWS resources users can access. Hence, it becomes easier to identify who is authenticated and authorized to use resources.

Some benefits IAM provides to businesses are as follows:

• Better security: IAM ensures that only authorized users have access to AWS resources.
• Better collaboration: IAM allows to easily share resources with other team members all the while maintaining the control over access permissions.
• More control: IAM provides well defined permissions to have greater control over who has access to which resources.
• Cost savings: As IAM prevents unnecessary resource usage, it leads to cost savings for your business.

Amazon Route 53 is a DNS service that provides businesses and developers a safe way to route traffic to the applications. For this, Amazon Route 53 translates domain names into numeric IP addresses. Route 53 also manages network traffic globally and builds highly available applications.

Route 53 provides features such as domain registration, health checks, traffic routing policies, and DNS query logging. It is designed to provide high availability and low latency for queries, with a global network of DNS servers located in multiple regions around the world.

Cloudtrail is a service that provides security monitoring, troubleshooting, and auditing through API and user tracking. It captures information for every request that is sent to Amazon Route 53 API by an AWS account. Moreover, Cloudtrail saves the information about requests sent to IAM users. CloudTrail logs include information about who made the API call, when the API call was made, the source IP address of the request, and other details.

When an AWS account makes requests to Amazon Route 53 by IAM users, CloudTrail records it. The request log files then generated are saved by CloudTrail in an Amazon s3 bucket.

LatencyBased Routing uses latency measurements between the AWS datacenters and user networks. Whereas, the Geo DNS bases routing decisions on the geographic location from where the request is made.

A domain is a collection of data and has easily recognizable names for numerically addressed Internet resources. Whereas, a hosted zone is a container to hold information and it is analogous to a traditional DNS zone file.

Amazon Route 53 is highly preferred for low latency and high availability due to the following reasons:

• Globally Distributed Servers: shorten the distance between the user and the resource.
• High level of dependability: to maintain a DNS service
• Highly Available and Reliable: Can direct customers reliably to online apps
• Flexible: Can manage traffic through various routes

Yes, Users can also use a delegated admin account to aggregate data from all the member accounts in AWS organizations without any additional authorization. With this, different teams in a company can use separate accounts, and aggregate organization-wide data in their respective administration accounts for centralized governance.

Reserved and on-demand DB instances are the same by function but differ in how they are billed. Reserved DB instances come with a discount compared to on-demand DB instance pricing.

This is one of the most common AWS interview questions hiring managers ask, especially at the advanced level. Vertical scaling and horizontal scaling are the two types of scaling that can be used for RDS. In vertical scaling, users can add more capacity to storage and compute on current RDS instances. Moreover, it is suitable if users can’t change their application and database connectivity configuration. Whereas, horizontal scaling refers to adding an RDS instance for reads and writes, and it also increases performance by extending the database operations to additional nodes.

It helps decide when DB instance modifications, version upgrades to the database engine, and software patching have to occur.

The two types of consistency models in DynamoDB are as follows:

• Eventual Consistency Model: This model indicates that the data store is highly available. his model provides the highest level of availability and the lowest latency.
• Strong Consistency Model: This model indicates that the data should be consistent always. This model ensures that all replicas of a data item are updated before a read operation returns

Amazon DynamoDB is a NoSQL database service. DynamoDB is a fully managed service, offering predictable and rapid performance to run highly-performant applications at scale. DynamoDB is highly preferred as it supports flexible querying, along with GET/PUT operations through a user-defined primary key. Furthermore, DynamoDB delivers apps with consistent single-digit millisecond performance and automatic multi-Region replication. It secure users data with encryption at rest, automatic backup and guaranteed reliability.

Simple Email Service (SES) is an Amazon service that delivers high-volume emails to customers. SES reaches at the customer inboxes as a trusted sender with secure email authentication. It also supports a variety of deployments including dedicated, shared, or owned IP addresses. Moreover, Amazon SES keeps users up-to-date by sending automated emails, such as purchase or shipping notifications, order status updates and policy change notices.

Simple Queue Service (SQS) is an Amazon-provided service that provides users with quick and reliable message queuing. Using SQS, messages are queued temporarily until the user wants to send them to consumers, thus removing overhead with no upfront cost. Moreover, SQS helps to communicate sensitive data securely between applications.

Simple Notification Service is a web service provided by Amazon to manage the delivery of messages to recipients. SNS delivers application-to-application (A2A) notifications and allows them to integrate and decouple distributed applications. Here, users can simplify their architecture and reduce costs with message filtering, ordering, batching, and deduplication.

Amazon ElastiCache is a web service managing the memory caching environment, boosting application performance, reducing latency to microseconds and decreasing overall costs. ElasticCache is compatible with both Redis or Memcached, users can build with their choice. Cache your data to reduce pressure on your backend database.

Following are the benefits of using ElastiCache:

1. Scalable Caching Environment: ElastiCache is a fully managed solution that can scale in-memory cache environment in cloud
2. High-Performance: ElastiCache reduces latency to improve the performance of the database providing high throughput.
3. Cost-effective depending on the scale it is used
4. Eases backend database load
5. Builds low-latency data stores.

Lambda Edge is a feature of Amazon CloudFront that lets you run code closer to users, avoiding any unnecessary latency, and thus, improving performance. Using Lambda Edge, users don’t have to manage infrastructure in multiple locations around the world. Moreover, Lambda Edge helps users enrich their web applications by making them globally distributed and improving their performance.

Amazon DynamoDB would be the ideal option for developing a game with low latency. DynamoDB provides fast performance with good scalability. Therefore, it can be used to create a table to handle a large number of traffic, and store or call back any amount of data. DynamoDB achieves this by distributing the traffic and data over a number of servers. It focuses on innovation and optimizing costs with a fully managed serverless database that automatically scales up and down to fit your needs.

Amazon CloudWatch is an excellent service that helps in real-time monitoring of AWS services. CloudWatch allows you to track the metrics of your resources and applications, and you can view them on the CloudWatch home page. CloudWatch also improves operational performance through alarms and automated actions that set to activate at some predefined thresholds.

For an ML engineer trying to implement a solution for finding sensitive information, Amazon Macie would be an ideal option. Amazon Macie is a security monitoring tool that uses AWS’s AI engine for classifying and analyzing content in Amazon S3 buckets. Macie uses machine learning and pattern matching to help secure sensitive data.

AWS IAM is an ideal choice for system administrators. IAM allows users to secure control and manage permissions of the resources users can access, including authentication and authorization. This service grants temporary security credentials for workloads that access users’ AWs resources. It manages identities across single AWS accounts or centrally connects identities to multiple AWS accounts.

Amazon VPC can help allocate private and public IP addresses, also making them interact with other instances, including the internet. This is because VPC allows AWS resource allocation in a user-defined virtual network. This service monitors connections, screen traffic, and restricts instance access inside the user virtual network. Moreover, VPC can customize users virtual network by choosing user IP address range, creating subnets and configuring route tables.

Amazon RDS helps to set up, operate, and scale the relational database engines in the cloud with users choice. Hence, it makes the perfect choice for resizable capacity, cost-efficiency, and automating tedious administration tasks.

Amazon Mechanical Turk is helpful for accessing consultants or human researchers, as it is a crowdsourcing marketplace. Using Mechanical Turk, individuals and organizations can seamlessly outsource their jobs to a distributed workforce who can perform these tasks virtually. Mechanical Turk also optimizes efficiency, increase flexibility and reduce costs.

Amazon Elastic Container Service (ECS) builds container-based applications and launches thousands of containers across the cloud. Users can automatically scale and run web applications in multiple availability zones with the performance, reliability, scale, and availability of AWS.

AWS Lambda can help users run code without managing servers as it is a serverless computing platform. One only needs to put code on Lambda for it to run. It writes, upload code as a zip file or container image, and runs the code without provisioning and managing infrastructure. Also, Lambda can work with any scale of code execution requests.

Amazon SQS is a pay-per-use service that helps users manage messages between software components. SQS allows users to decouple and scale web services together using queues in a very simple and reliable way. It ensures users that the work is completed on time and cost- effectively. Moreover, SQS allows users to deduplicate messages while maintaining the message order and process messages at high scale. In banking applications, SQS separates front-end from back-end systems, processes bill payments in the background, and still offers customers immediate responses.

Amazon Chime is ideal for hosting real-time audio and video conferencing applications on AWS. Chime is a communication service that lets users chat, meet, and place business calls inside and outside your company, all using a single application. Users can conduct and attend online meetings with screen sharing, dial-in numbers, meeting chat, and in-room video conference support. With the help of Amazon Chime, administer enterprise users can manage policies and set up SSO or other latest features in a very short period of time.

AWS Batch lets users create a range of similar individual jobs. AWS Batch is a batch computing service that helps developers, scientists and engineers easily perform batch computing operations on AWS quickly and effectively. Thanks to AWS it is not necessary to operate a third- party commercial or open-source batch processing system. Batch helps users to take advantage of the services without any hassle about setting up and managing the required infrastructure.

Amazon CloudSearch is a cloud service that acts as a simple, cost effective and scalable search solution for your website. CloudSearch helps to bring various sorts of seek and fetch abilities to your application and supports 34 languages and popular search features such as autocomplete, highlighting, and geospatial search. Plus, CloudSearch helps you add rich search capabilities to your website.

AWS Certificate Manager is an administrative feature that helps you provision, deploy, and manage public and private Secure Socket Layers. These layers are used with AWS services for internally connected resources.

An Auto Scaling group contains a selection of EC2 instances that are treated as groups for automatic scaling and management. Auto Scaling is a service that helps the user closely monitor applications and automatically adjusts their capacity for better, steady, predictable performance at the lowest possible cost. There are many benefits of Auto Scaling such as better cost management, fault tolerance, high availability, reliability and flexibility of resources. Users must remember that they need to create a backup and store data in Auto Scaling.