AWS Interview Questions for Amazon Jobs: S3, Cloud Services and Key Topics

AWS Fundamentals Interview Questions

Interviewers almost always start here to gauge whether you understand the basic building blocks before moving into specifics.

What is AWS and why do companies use it?

AWS, or Amazon Web Services, is a cloud computing platform offering on demand compute, storage, networking, and database services billed on a pay as you go basis. Companies use it to avoid the upfront cost and lead time of buying physical servers, and to scale infrastructure up or down based on actual demand rather than guessing capacity months in advance.

What is the difference between a Region and an Availability Zone?

A Region is a distinct geographic area, such as us-east-1, that contains multiple isolated data centers. An Availability Zone is one of those individual data centers within a Region, and running your application across multiple Availability Zones protects it from a single data center failure taking your whole system down.

What is the AWS Shared Responsibility Model?

The Shared Responsibility Model defines where AWS's security obligations end and the customer's begin. AWS is responsible for security of the cloud, meaning the physical infrastructure, hardware, and foundational services, while the customer is responsible for security in the cloud, meaning how they configure access controls, encryption, and network settings on their own resources.

What is the difference between horizontal and vertical scaling in AWS?

Vertical scaling means increasing the resources of a single instance, such as moving to a larger EC2 instance type with more vCPU and memory. Horizontal scaling means adding more instances running in parallel, typically behind a load balancer, which is generally the preferred approach in AWS since it avoids a hard ceiling on capacity and improves fault tolerance.

AWS S3 Interview Questions

S3 comes up in nearly every AWS interview because it is foundational to how storage works across the entire platform.

What is Amazon S3 and what is it used for?

Amazon S3, or Simple Storage Service, is an object storage service used to store and retrieve any amount of data, such as files, backups, images, and static website content, accessed through a simple key based structure rather than a traditional file system.

What are S3 storage classes and how do they differ?

S3 currently offers eight storage classes, each built around a different balance of access frequency, durability, and cost.

How does S3 achieve high durability?

S3 Standard is designed for eleven nines of durability, meaning 99.999999999 percent, achieved by automatically storing redundant copies of your data across multiple Availability Zones within a Region, so the loss of an entire data center does not mean losing your data.

What is the difference between S3 and EBS?

S3 is object storage accessed over HTTP, ideal for storing files independently of any specific server. EBS, Elastic Block Store, is block storage attached directly to a single EC2 instance, functioning more like a traditional hard drive that the operating system interacts with directly.

How would you secure an S3 bucket?

A properly secured S3 bucket typically combines bucket policies to control who can access it, IAM policies to control what specific users or roles can do, blocking public access at the account or bucket level unless explicitly required, enabling server side encryption for data at rest, and using S3 access logging or CloudTrail to monitor activity against the bucket.

What is S3 versioning and why would you enable it?

Versioning keeps every version of an object as it is overwritten or deleted, rather than replacing it permanently. This protects against accidental deletion or overwrite, since you can restore an earlier version, though it also means storage costs grow as old versions accumulate unless you pair it with a lifecycle policy.

AWS Compute and EC2 Interview Questions

What is Amazon EC2?

EC2, Elastic Compute Cloud, provides resizable virtual servers in the cloud, letting you choose the operating system, instance type, and storage configuration, and scale the number of running instances up or down based on demand.

What is the difference between an EC2 instance and a container?

An EC2 instance is a full virtual machine with its own operating system kernel, while a container shares the host operating system's kernel and packages just the application and its dependencies, making containers lighter weight and faster to start than a full instance.

What is Auto Scaling and how does it work?

Auto Scaling automatically adjusts the number of running EC2 instances based on defined conditions, such as CPU utilization crossing a threshold, ensuring your application has enough capacity during traffic spikes without paying for idle instances during quiet periods.

What is the difference between an Application Load Balancer and a Network Load Balancer?

An Application Load Balancer operates at the application layer and can route traffic based on content like URL paths or hostnames, making it well suited to web applications. A Network Load Balancer operates at the transport layer, handling extremely high throughput with ultra low latency, and is better suited to workloads needing raw TCP performance rather than content based routing.

AWS Security and IAM Interview Questions

Security questions test whether you understand access control, not just how to launch resources.

What is IAM and why does it matter?

IAM, Identity and Access Management, controls who can access AWS resources and what actions they are allowed to perform. It matters because misconfigured permissions are one of the most common sources of real world cloud security incidents, far more often than a flaw in AWS's own infrastructure.

What is the difference between an IAM role and an IAM user?

An IAM user represents a specific person or application with long term credentials. An IAM role is an identity that can be assumed temporarily, commonly by an EC2 instance, Lambda function, or another AWS account, without requiring long term credentials to be stored anywhere, which is generally the more secure pattern.

What is the principle of least privilege and how do you apply it in AWS?

Least privilege means granting only the specific permissions required to perform a task, nothing more. In practice, this means writing narrowly scoped IAM policies instead of using broad managed policies like AdministratorAccess, and regularly auditing permissions to remove access that is no longer needed.

How would you rotate credentials securely in AWS?

Rather than hardcoding long lived access keys, the more secure pattern is using IAM roles for applications running on AWS resources, since roles issue short lived, automatically rotated credentials. For actual IAM users that need access keys, AWS supports scheduled key rotation, and Secrets Manager can automate rotation for things like database credentials.

AWS Cloud Architecture and Deployment Questions

How would you design a highly available application on AWS?

A typical answer covers distributing EC2 instances across multiple Availability Zones behind a load balancer, using Auto Scaling to handle variable traffic, storing session data outside individual instances so any instance can serve any request, and using a managed database with multi-AZ replication such as RDS or Aurora for the data layer.

What is the difference between a VPC and a subnet?

A VPC, Virtual Private Cloud, is an isolated virtual network within AWS that you fully control. A subnet is a smaller segment within that VPC, tied to a specific Availability Zone, typically split into public subnets for internet facing resources and private subnets for resources that should not be directly reachable from the internet.

What is the difference between CloudFormation and Terraform?

CloudFormation is AWS's native infrastructure as code service, describing resources in JSON or YAML templates specifically for AWS. Terraform is a third party, cloud agnostic tool that supports AWS alongside other providers, using its own configuration language, which makes it a common choice for teams managing infrastructure across multiple cloud providers.

Conclusion

Most AWS interviews, whether focused specifically on S3 or covering the broader platform, reward candidates who can explain not just what a service does, but why you would choose it over an alternative and how it fits into a larger architecture. Reviewing questions like these is a good starting point, but the strongest preparation comes from actually building something small in an AWS free tier account, since hands on experience with services like S3, EC2, and IAM makes these answers come naturally instead of sounding memorized. Spend some time in the console building a simple project before your interview, and revisit any topic here that felt shaky.