AWS Interview Questions and Answers for experienced

1. What are the core AWS services and how do they interact?

   • Answer: Core AWS services include Compute (EC2, Lambda), Storage (S3, EBS, Glacier), Database (RDS, DynamoDB, Redshift), Networking (VPC, Route 53, CloudFront), and Management Tools (CloudWatch, CloudTrail). They interact to form a complete solution. For example, an application running on EC2 might store data in S3, use RDS for a relational database, and leverage CloudFront for content delivery. CloudWatch monitors the entire infrastructure's health and performance.

2. Explain the difference between EC2 and Lambda. When would you choose one over the other?

   • Answer: EC2 provides virtual servers you manage, offering complete control. Lambda is a serverless compute service; you write code, and AWS handles the infrastructure. Choose EC2 for applications requiring persistent infrastructure, control over OS, and complex configurations. Choose Lambda for event-driven architectures, microservices, and reducing operational overhead. Lambda is cost-effective for infrequent tasks.

3. Describe different AWS storage services and their use cases.

   • Answer: S3: Object storage for unstructured data (images, videos, backups). EBS: Block storage for EC2 instances (persistent storage for VMs). Glacier: Archival storage for long-term, infrequent access data. EFS: File system storage for EC2 instances (shared file system). S3 Glacier Deep Archive: Extremely low-cost archival storage for very infrequent access.

4. How does AWS handle security?

   • Answer: AWS employs a shared responsibility model. AWS secures the infrastructure, while the customer is responsible for securing their data and applications running on it. Security features include IAM (Identity and Access Management) for user access control, VPCs for network isolation, Security Groups and Network ACLs for firewall rules, KMS (Key Management Service) for encryption, and CloudTrail for auditing.

5. Explain the concept of IAM roles and policies.

   • Answer: IAM roles are virtual users that grant permissions to AWS services without requiring explicit credentials. Policies define what actions a user or role can perform. They use JSON-based statements specifying actions, resources, and conditions. Attaching a policy to a role or user grants those permissions.

6. What are different types of AWS databases and when would you use each?

   • Answer: RDS: Managed relational databases (MySQL, PostgreSQL, Oracle, SQL Server). DynamoDB: NoSQL key-value and document database. Redshift: Data warehousing service for large-scale data analysis. Aurora: MySQL and PostgreSQL-compatible relational database service with high performance and availability. DocumentDB: MongoDB-compatible document database.

7. Describe AWS Elastic Beanstalk.

   • Answer: Elastic Beanstalk is a service that simplifies deploying and managing web applications and services on AWS. It handles capacity provisioning, load balancing, scaling, and application health monitoring, abstracting away much of the underlying infrastructure management.

8. Explain the different types of Amazon EC2 instance types.

   • Answer: EC2 offers various instance types optimized for different workloads: general-purpose, compute-optimized, memory-optimized, accelerated computing (GPU), storage-optimized. Each type has varying CPU, memory, and storage configurations to best suit specific applications.

9. How does AWS handle scaling?

   • Answer: AWS offers various scaling mechanisms. Auto Scaling automatically adjusts the number of EC2 instances based on metrics like CPU utilization or request count. Application Load Balancers distribute traffic across multiple instances. Lambda scales automatically based on the number of events.

10. What is AWS CloudFormation?

    • Answer: CloudFormation is a service for provisioning and managing AWS resources using infrastructure-as-code. You define a template (YAML or JSON) describing your infrastructure, and CloudFormation creates and manages those resources.

11. Explain the concept of a VPC (Virtual Private Cloud).

    • Answer: A VPC is a logically isolated section of the AWS Cloud, providing a virtual network for your resources. It allows you to customize your network configuration (subnets, routing tables, security groups) and provides enhanced security and isolation.

12. What is Amazon SQS (Simple Queue Service)?

    • Answer: SQS is a message queuing service that enables decoupled communication between different components of an application. It allows for asynchronous processing and improves scalability and reliability.

13. What is Amazon SNS (Simple Notification Service)?

    • Answer: SNS is a pub/sub messaging service used for sending messages to many subscribers. It's used for fan-out notifications, such as alerting, mobile push notifications, and event-driven architectures.

14. Describe AWS CloudWatch.

    • Answer: CloudWatch is a monitoring and logging service for AWS resources and applications. It collects metrics, logs, and events, allowing you to track the performance and health of your infrastructure and applications.

15. What is AWS CloudTrail?

    • Answer: CloudTrail provides a record of API calls made to your AWS account. It's used for security auditing, compliance, and troubleshooting.

16. Explain the difference between a Security Group and a Network ACL.

    • Answer: Security Groups are stateful, instance-level firewalls that control inbound and outbound traffic to EC2 instances. Network ACLs are stateless, subnet-level firewalls that control traffic at the subnet level.

17. What are AWS Elastic Load Balancers (ELBs)?

    • Answer: ELBs distribute incoming traffic across multiple EC2 instances, ensuring high availability and scalability. They support different load balancing algorithms and health checks.

18. What is AWS Route 53?

    • Answer: Route 53 is a highly available and scalable DNS web service. It allows you to map domain names to your AWS resources.

19. What is AWS CloudFront?

    • Answer: CloudFront is a content delivery network (CDN) that caches content closer to users, improving performance and reducing latency.

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