Top 50 AWS Interview Questions and Answers 2025 Guide
Beginner-Level AWS Interview Questions
These questions help interviewers check your fundamentals.
1. What is AWS? Why is it so popular?
Answer: AWS (Amazon Web Services) is a cloud platform that provides on-demand services like compute, storage, databases, networking, and security. It is popular because it offers:
- Pay-as-you-go pricing
- Global data centers
- High availability
- 200+ fully managed services
- Strong security standards
2. What is Cloud Computing?
Answer: Cloud computing allows you to access computing resources (servers, storage, databases) over the internet instead of owning physical hardware.
3. What are the core services of AWS?
Answer:
Compute: EC2, Lambda
Storage: S3, EBS
Database: RDS, DynamoDB
Networking: VPC, Route 53
Security: IAM, KMS
4. What is an EC2 instance?
Answer: EC2 is a virtual server in AWS used to run applications. You can choose CPU, memory, storage, and network capacity based on your needs.
5. What are the EC2 instance types?
Answer:
- General Purpose (t3, m6i)
- Compute Optimized (c6g)
- Memory Optimized (r6g)
- Storage Optimized (i3)
- Accelerated Computing (p4, g5)
6. What is S3?
Answer: Amazon S3 is object storage used to store files like images, videos, logs, and backups with 11 nines durability.
7. What is the difference between S3 Standard and Glacier?
Answer:
S3 Standard: Frequently accessed data
Glacier: Archival storage with slow retrieval
8. What is IAM?
Answer: IAM (Identity and Access Management) is a service in AWS that helps you manage who is allowed to access your resources and what specific actions they are permitted to perform.
9. IAM User vs IAM Role?
Answer: An IAM User is typically created for an individual and comes with long-term credentials, such as a username and password, allowing the person to directly access AWS resources. In contrast, an IAM Role is designed for services or applications and provides temporary credentials without a password, enabling secure access to resources without being tied to a specific person.
10. What is a VPC?
Answer: A Virtual Private Cloud is your private network in AWS where you can launch EC2 instances, subnets, and control traffic.
11. What is a subnet?
Answer: A small section inside a VPC, used to organize resources into public and private networks.
12. What is the difference between Security Groups and NACLs?
Answer: A Security Group is stateful and operates at the instance level, meaning that if you allow traffic in, the response is automatically allowed. Security groups support only allow rules. On the other hand, a Network ACL (NACL) is stateless and works at the subnet level, requiring explicit rules for both inbound and outbound traffic, and it supports both allow and deny rules.
13. What is CloudWatch?
Answer: A monitoring service that tracks logs, metrics, and alarms for AWS resources.
14. What is Auto Scaling?
Answer: Automatically increases or decreases EC2 instances based on demand.
15. What is AWS Lambda?
Answer: A serverless compute service that runs code without managing servers. You only pay when your code runs.
Intermediate-Level AWS Interview Questions
16. What triggers can invoke a Lambda function?
Answer:
- S3
- API Gateway
- CloudWatch Events
- SQS/SNS
- DynamoDB Streams
- EventBridge
17. What are the types of Elastic Load Balancer?
Answer:
- Application Load Balancer (ALB)
- Network Load Balancer (NLB)
- Classic Load Balancer (CLB)
18. What is Amazon RDS?
Answer: A fully managed relational database service with automated:
- Backups
- Patching
- Failover
- Replication
19. What is DynamoDB?
Answer: A NoSQL key-value database that provides:
- Single-digit millisecond latency
- Auto scaling
- Serverless architecture
20. What is Route 53?
Answer: AWS’s DNS service is used for domain registration, routing, and health checks.
21. What is CloudFront?
Answer: A Content Delivery Network (CDN) that delivers content faster using global edge locations.
22. What is the AWS Shared Responsibility Model?
Answer:
AWS: Manages the security of the cloud
Customer: Manages security in the cloud
23. What is Amazon EBS?
Answer: Elastic Block Store provides block storage for EC2 instances.
24. What is S3 Versioning?
Answer: Keeps multiple versions of objects to protect against accidental deletion or overwrites.
25. What is AWS KMS?
Answer: Key Management Service is used for encryption and secure key storage.
26. What is Amazon SNS?
Answer: It is a messaging service based on the publish–subscribe model that allows you to deliver notifications to many subscribers at the same time.
27. What is Amazon SQS?
Answer: A fully managed message queue used to decouple applications.
28. What is Elastic Beanstalk?
Answer: A managed service that automatically deploys and scales applications.
29. What is AWS Fargate?
Answer: A serverless compute engine for running containers without managing servers.
30. What is AWS Organizations?
Answer: Allows you to manage multiple AWS accounts under one umbrella.
31. What is Amazon ECR?
Answer: A fully managed container registry for storing Docker images.
32. What is Amazon ECS?
Answer: Elastic Container Service for running containers at scale.
33. What is Multi-AZ in RDS?
Answer: Provides automatic failover to a standby database for high availability.
34. What is Terraform vs CloudFormation?
Answer:
Terraform: Multi-cloud IaC tool
CloudFormation: AWS-native IaC
35. What is the AWS Well-Architected Framework?
Pillars:
- Operational Excellence
- Security
- Reliability
- Performance Efficiency
- Cost Optimization
- Sustainability
Advanced-Level AWS Interview Questions
36. What is the difference between Horizontal and Vertical Scaling?
Answer:
Vertical: Increasing the size (CPU/RAM) of a single instance
Horizontal: Increasing the number of instances
37. What is AWS Global Accelerator?
Answer: Improves the performance of global applications using AWS edge networks.
38. What is VPC Peering?
Answer: Connects two VPCs to communicate privately.
39. What is Transit Gateway?
Answer: A hub-and-spoke model to connect multiple VPCs and on-premises networks.
40. What is S3 Lifecycle Management?
Answer: Automates moving objects between storage classes to reduce cost.
41. What is AWS Redshift?
Answer: A fully managed data warehouse used for analytics and BI workloads.
42. How does AWS ensure high availability?
Answer:
- Multi-AZ
- Auto-scaling
- Load balancing
- Global infrastructure
43. What is an AMI?
Answer: Amazon Machine Image is used to launch EC2 instances with pre-configured OS and software.
44. What is Spot, Reserved, and On-Demand EC2 pricing?
Answer:
- On-Demand: Pay-as-you-go
- Reserved: 1–3 year commitment
- Spot: Cheapest, uses unused capacity
45. What is AWS Backup?
Answer: A centralized backup service for EC2, RDS, EFS, DynamoDB, and more.
46. What is EKS?
Answer: Amazon’s managed Kubernetes service.
47. What is AWS WAF?
Answer: A Web Application Firewall that protects against common web attacks.
48. What is Cross-Region Replication in S3?
Answer: Automatically replicates objects to another region for disaster recovery.
49. What is AWS IAM Policy?
Answer: A JSON document that defines permissions for users, roles, and services.
50. How do you secure an EC2 instance?
Answer:
- Enable IAM roles
- Use Security Groups
- Encrypt volumes
- Patch OS
- Disable root SSH access
- Use Key Pairs
Conclusion
Cracking an AWS interview in 2025 becomes much easier when you understand the core cloud concepts, practice real-world scenarios, and stay updated with the latest AWS services. These top 50 AWS interview questions give you a strong foundation and help you approach interviews with confidence.
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