AWS Interview Questions and Answers (Beginner to Advanced)

Practice the Most Common and Critical Questions for AWS Roles – with Detailed Answers and Explanations

Whether you’re aiming for a cloud engineer role or preparing for AWS certification, interviews often test not just your knowledge, but your practical understanding.

This chapter is divided into:

🟢 Beginner-Level Questions

🟡 Intermediate-Level Questions

🔴 Advanced-Level + Scenario-Based Questions

🟢 Beginner-Level AWS Interview Questions

1. What is AWS?

Answer:
Amazon Web Services (AWS) is a cloud platform that offers over 200 services like compute, storage, networking, databases, and security tools to build scalable applications.

2. What are the key benefits of AWS?

Answer:

• Pay-as-you-go pricing
• Scalability & elasticity
• Global infrastructure (Regions & AZs)
• High availability
• Built-in security and compliance

3. What is EC2 in AWS?

Answer:
Amazon EC2 (Elastic Compute Cloud) is a virtual server used to run applications. You can choose instance type, OS, storage, and networking configuration.

4. What is S3 in AWS?

Answer:
Amazon S3 (Simple Storage Service) is an object storage service that allows you to store unlimited data as objects in buckets with high availability and durability (99.999999999%).

5. Explain the AWS Free Tier.

Answer:
AWS offers a 12-month Free Tier which includes:

• 750 hours/month of EC2 (t2.micro)
• 5 GB of S3 storage
• 25 GB DynamoDB
• 1 million Lambda invocations

6. What is IAM?

Answer:
AWS Identity and Access Management (IAM) allows you to manage users, roles, and policies to securely control access to AWS services and resources.

🟡 Intermediate-Level AWS Interview Questions

7. What is the difference between an AMI and an EC2 instance?

Answer:

• AMI (Amazon Machine Image) is a template for launching EC2 instances.
• EC2 instance is a running virtual server based on an AMI.

8. How does Auto Scaling work in AWS?

Answer:
Auto Scaling automatically adjusts the number of EC2 instances in response to load conditions (CPU, memory, or custom metrics). It ensures high availability and cost-efficiency.

9. Difference between Security Groups and Network ACLs?

10. What is the use of Route 53 in AWS?

Answer:
Route 53 is a scalable DNS and domain name registration service. It can:

• Route traffic globally with latency-based routing
• Act as a domain registrar
• Perform health checks for failover routing

11. What is the difference between RDS and DynamoDB?

12. Explain the AWS Shared Responsibility Model.

Answer:
AWS secures the infrastructure (hardware, network, data centers), while customers are responsible for securing the data, IAM policies, applications, and firewall configurations.

13. What is CloudFormation?

Answer:
CloudFormation allows you to model and provision AWS infrastructure using code (JSON or YAML templates), also known as Infrastructure as Code (IaC).

🔴 Advanced/Scenario-Based AWS Interview Questions

14. How would you design a fault-tolerant, high-availability web app on AWS?

Answer:

• Use ALB to distribute traffic across Auto Scaling Groups in multiple AZs
• Store assets in S3 with CloudFront
• Use RDS Multi-AZ or Aurora
• Backup using S3 Lifecycle + CloudWatch
• Monitor via CloudWatch & GuardDuty

15. Explain VPC peering and its limitations.

Answer:
VPC peering connects two VPCs privately without routing traffic over the public internet.
Limitations:

• No transitive peering
• Must update route tables manually
• CIDR ranges must not overlap

16. How does S3 ensure data durability?

Answer:
S3 redundantly stores data across multiple AZs. It provides 99.999999999% durability (11 9s) through automatic replication and integrity checks.

17. What are Placement Groups in EC2?

Answer:

• Cluster: Low latency, high throughput (same AZ)
• Spread: Instances on different hardware (fault tolerance)
• Partition: Grouped into partitions, fault isolation in large deployments

18. How do you secure sensitive data in DynamoDB?

Answer:

• Enable encryption at rest (KMS)
• Use IAM policies for table access
• Implement VPC endpoints
• Enable fine-grained access control
• Use CloudTrail for audit logging

19. How would you migrate a legacy monolithic app to AWS?

Answer:

1. Rehost (lift-and-shift) to EC2
2. Replatform to Docker/ECS or Elastic Beanstalk
3. Refactor into microservices with API Gateway + Lambda
4. Use CodePipeline for CI/CD
5. Store DB in RDS or Aurora

20. What is a use case for AWS Transit Gateway?

Answer:
When you have multiple VPCs and on-prem networks, Transit Gateway acts as a hub to manage interconnectivity efficiently—avoiding VPC peering complexity.

Bonus Questions (for Senior Roles)

• How do you enforce S3 bucket policies across your entire org?
• How does AWS Cognito differ from IAM?
• What are lifecycle policies in EC2 or S3?
• Compare ECS and EKS: When would you use each?
• Explain how AWS Systems Manager helps in fleet-wide operations.