Interview Prep Guide

AWS Interview Questions and Answers for Freshers to Experienced Developers

Prepare for AWS interviews with questions on core services, networking, scaling, security, architecture choices, and practical system design.

Basic AWS Interview Questions

  1. What is the difference between a Region and an Availability Zone in AWS?

    A Region is a geographic area containing multiple Availability Zones, and an Availability Zone is an isolated data-center cluster within a Region.

  2. What are EC2, S3, and IAM used for?

    EC2 provides virtual compute, S3 provides object storage, and IAM manages identity, access, and permissions in AWS.

  3. What is the difference between a public subnet and a private subnet?

    A public subnet has routing that can reach the internet through an internet gateway, while a private subnet is intended for internal resources that should not be directly reachable from the public internet.

  4. What is the difference between EBS and S3?

    EBS (Elastic Block Store) is block storage used like a hard drive for an EC2 instance, while S3 (Simple Storage Service) is object storage used for storing and retrieving files over the web.

  5. What is the Shared Responsibility Model in AWS?

    It defines that AWS is responsible for the security "of" the cloud (infrastructure), while the customer is responsible for security "in" the cloud (data, OS configuration, IAM).

Medium AWS Interview Questions

  1. What is a VPC, and how do security groups fit into it?

    A VPC is a logically isolated virtual network in AWS, and security groups act like stateful virtual firewalls controlling inbound and outbound traffic for resources.

  2. How do load balancers and auto scaling help an application?

    Load balancers distribute traffic across healthy targets, while auto scaling adjusts compute capacity based on demand or health signals.

  3. How would you choose between RDS and DynamoDB for an application?

    Choose based on data model, access patterns, consistency and relational needs, operational trade-offs, and how predictable the workload is.

  4. What is the difference between SQS and SNS?

    SQS (Simple Queue Service) is a message queue for decoupled one-to-one communication, while SNS (Simple Notification Service) is a pub/sub system for one-to-many broadcasting.

  5. What are CloudWatch and CloudTrail used for?

    CloudWatch is for monitoring performance metrics and logs, while CloudTrail is for auditing API calls and account activity.

Advanced AWS Interview Questions

  1. How would you choose between EC2, containers, and Lambda?

    Choose based on operational control, scaling pattern, runtime flexibility, cold-start tolerance, and team maturity rather than treating one option as universally best.

  2. What is Blue/Green deployment and how can you do it in AWS?

    Blue/Green deployment is a strategy where you deploy the new version (Green) alongside the old one (Blue), then switch traffic all at once or gradually.

  3. What is AWS CloudFront and what are its benefits?

    CloudFront is a Content Delivery Network (CDN) that caches content at Edge Locations to reduce latency and improve load times globally.

Scenario-Based AWS Interview Questions

  1. How would you approach an AWS system that works functionally but has rising cost, weak observability, and unclear scaling behavior?

    Treat it as an architecture review: identify which services drive cost, where scaling is unpredictable, and where monitoring or alarms are missing before changing services blindly.

AWS Practical Round

  1. Design a scalable architecture for a public API or static-site-plus-API product

    These rounds are often discussion-based rather than pure coding. A good answer starts with traffic pattern and requirements, then chooses storage, compute, networking, and monitoring deliberately instead of naming every AWS service at once.

  2. Identify the AWS CLI command to list and filter S3 buckets

    A basic command is aws s3 ls . For more advanced listing or filtering, candidates should mention aws s3api list-buckets and using --query to focus on specific fields. Knowing the CLI shows practical operational experience.

  3. Design a small cloud workflow for uploads, background processing, storage, and monitoring

    Interviewers usually want a practical design more than a list of services. Strong answers explain why each service is chosen, what failure modes are considered, and how the flow is monitored once it reaches production.