These aws interview questions and answers span freshers to experienced cloud engineers — covering EC2, S3, IAM, VPC, auto scaling, load balancing, Lambda and the shared responsibility model — each with a concise, correct model answer to adapt in your own words.
Beginner aws interview questions
Q: What is the difference between a Region and an Availability Zone?
A: A Region is a separate geographic area, such as Mumbai, containing multiple isolated data centres. An Availability Zone is one or more discrete data centres within a Region with independent power and networking. You deploy across multiple Availability Zones for high availability and choose Regions for latency, cost and data-residency needs.
Q: What is Amazon EC2?
A: EC2, Elastic Compute Cloud, provides resizable virtual servers called instances. You choose an instance type for CPU and memory, an Amazon Machine Image for the operating system, and pay per second or hour. It is the core compute service for running applications when you need control over the operating system.
Q: What is Amazon S3?
A: S3, Simple Storage Service, is object storage for files of almost any size, organised into buckets with high durability across multiple Availability Zones. It is used for backups, static websites, data lakes and media. It offers storage classes at different price and access speeds, and access is controlled by policies rather than a filesystem.
Q: What is IAM?
A: IAM, Identity and Access Management, controls who can do what in your account. It manages users, groups, roles and policies that grant least-privilege permissions to services and people. Roles are especially important because they let services and EC2 instances obtain temporary credentials instead of hard-coded keys.
Q: What is the AWS shared responsibility model?
A: AWS is responsible for security of the cloud — the hardware, networking and managed service infrastructure. The customer is responsible for security in the cloud — configuring services, managing IAM, encrypting data, patching guest operating systems and setting network rules. The split shifts depending on how managed a service is.
Q: What is the difference between horizontal and vertical scaling?
A: Vertical scaling means resizing to a larger instance with more CPU or memory, which has limits and usually needs downtime. Horizontal scaling means adding more instances behind a load balancer, which AWS favours because it improves availability and fault tolerance. Auto Scaling automates horizontal scaling based on demand.
Intermediate aws interview questions
Q: What is a VPC?
A: A VPC, Virtual Private Cloud, is your logically isolated network within AWS where you define IP ranges, subnets, route tables and gateways. Public subnets reach the internet through an internet gateway; private subnets stay internal and use a NAT gateway for outbound access. It gives you control over network topology and security.
Q: What is the difference between a security group and a network ACL?
A: A security group is a stateful firewall at the instance level; if you allow inbound traffic, the response is automatically allowed. A network ACL is a stateless firewall at the subnet level that evaluates inbound and outbound rules separately. Security groups only allow rules; ACLs can also explicitly deny.
Q: What is Auto Scaling?
A: Auto Scaling automatically adjusts the number of EC2 instances in a group to match demand, using policies tied to metrics like CPU utilisation. It maintains a desired capacity, replaces unhealthy instances and works with a load balancer. This keeps applications available under load while controlling cost during quiet periods.
Q: What is Elastic Load Balancing and what are the types?
A: ELB distributes incoming traffic across multiple targets for availability and scale. The Application Load Balancer works at layer seven for HTTP and HTTPS with content-based routing. The Network Load Balancer works at layer four for very high performance and static IPs. The Gateway Load Balancer is for deploying network appliances.
Q: What is the difference between S3 and EBS?
A: S3 is object storage accessed over HTTP, ideal for files, backups and static content, and it is not attached to a single instance. EBS, Elastic Block Store, provides block volumes that attach to one EC2 instance like a disk, suited to operating systems and databases needing low-latency block access.
Q: What is Amazon RDS?
A: RDS, Relational Database Service, is a managed database service supporting engines like MySQL, PostgreSQL, MariaDB, Oracle and SQL Server. AWS handles provisioning, patching, backups and replication, and Multi-AZ deployments provide failover. It reduces database administration compared with running a database yourself on EC2.
Q: What is the difference between stopping and terminating an EC2 instance?
A: Stopping shuts the instance down but keeps its EBS root volume, so you can start it again later and you stop paying for compute while still paying for storage. Terminating deletes the instance and, by default, its root volume, which is permanent. Use stop for pauses and terminate to remove for good.
Advanced aws interview questions
Q: What is AWS Lambda and when should you use it?
A: Lambda runs code in response to events without managing servers, scaling automatically and charging only for execution time. It suits short, event-driven tasks like processing S3 uploads, responding to API Gateway requests or reacting to queue messages. It is less suited to long-running or stateful workloads because of time and resource limits.
Q: What is an IAM role versus an IAM user?
A: An IAM user represents a person or application with long-term credentials. An IAM role is an identity with permissions but no permanent credentials; it is assumed temporarily, issuing short-lived tokens. Roles are best practice for EC2, Lambda and cross-account access because they avoid storing static keys.
Q: How do you design a highly available web application on AWS?
A: Deploy across at least two Availability Zones, place instances in an Auto Scaling group behind an Application Load Balancer, and use a Multi-AZ RDS database. Store static assets in S3, optionally front them with CloudFront, and keep configuration in private subnets. This removes single points of failure and scales with demand.
Q: What is the difference between SQS and SNS?
A: SQS is a message queue where consumers pull messages, decoupling producers from consumers and smoothing load. SNS is a pub or sub service that pushes messages to many subscribers such as queues, Lambda functions or endpoints. A common pattern fans out with SNS to multiple SQS queues for reliable parallel processing.
Q: What is CloudFormation?
A: CloudFormation is AWS’s infrastructure-as-code service that provisions resources from declarative templates in JSON or YAML. It creates and updates resources predictably as a stack, supports rollback on failure and makes environments reproducible. It reduces manual console work and lets infrastructure be version-controlled and reviewed like application code.
Q: How do you secure data at rest and in transit on AWS?
A: For data at rest, enable encryption using KMS-managed keys on services like S3, EBS and RDS. For data in transit, use TLS via HTTPS endpoints and certificates from ACM. Combine this with least-privilege IAM, private subnets and bucket policies so encryption is backed by strict access control.
Q: What is the difference between vertical scaling of RDS and a read replica?
A: Vertical scaling changes the RDS instance class for more capacity and affects both reads and writes but has an upper limit. A read replica is an asynchronous copy that offloads read traffic, improving read throughput and enabling reporting without burdening the primary. Replicas scale reads; they do not scale writes.
How to prepare for an AWS interview
Get hands-on in the free tier — launch an EC2 instance, host a static site on S3 and write an IAM policy — because interviewers can tell console experience from memorised definitions. Practise sketching a highly available architecture and explaining trade-offs. A Cloud Practitioner or Solutions Architect Associate certification helps you get shortlisted. Freshers should review the apprenticeship and Skill India guide, pair this with our Python interview questions for cloud scripting roles, and watch the GetJobsNews homepage for openings.
Frequently Asked Questions
How do I prepare for an AWS interview?
Learn the core services — EC2, S3, IAM, VPC, RDS and Lambda — and understand regions, availability zones, the shared responsibility model and auto scaling. Do hands-on labs in the free tier, and consider the Cloud Practitioner or Solutions Architect Associate certification. Be ready to design a simple, highly available architecture on a whiteboard.
Is AWS hard to learn for freshers?
AWS has a large service catalogue, which feels overwhelming at first, but a fresher only needs the core dozen services to start. Hands-on practice in the free tier makes concepts click faster than reading. Focus on compute, storage, networking and identity, then expand. Most people become interview-ready in one to two months.
What AWS topics are asked most for freshers?
Freshers get the difference between EC2 and S3, what IAM does, regions versus availability zones, the shared responsibility model, and basic scaling with a load balancer. Expect a definition of common services and a simple scenario such as hosting a website or storing files reliably.
Which AWS certification helps for interviews?
The Cloud Practitioner is a good foundation for freshers, while the Solutions Architect Associate is the most respected entry-level technical certification and maps well to interview topics. Certifications get you shortlisted, but interviewers still expect hands-on understanding, so pair any certificate with real console and CLI practice.
