AWS Interview Questions and Answers for 5 years experience

1. What are the different AWS global regions and why are they important?

   • Answer: AWS has numerous global regions, each comprising multiple Availability Zones (AZs). These regions are geographically dispersed to ensure high availability, low latency, and data sovereignty compliance. Choosing the right region is crucial for performance, cost optimization, and adherence to regulations. Factors to consider include user proximity, data residency requirements, and supported services.

2. Explain the difference between EC2 and ECS.

   • Answer: Amazon EC2 (Elastic Compute Cloud) provides virtual servers (instances) where you can run your applications. Amazon ECS (Elastic Container Service) is a container orchestration service that manages containers (e.g., Docker) on EC2 instances or on AWS Fargate (serverless compute for containers). EC2 provides the underlying infrastructure, while ECS manages the deployment, scaling, and lifecycle of containerized applications.

3. Describe the different types of Amazon S3 storage classes.

   • Answer: S3 offers various storage classes optimized for different access patterns and cost considerations. These include Standard (frequent access), Intelligent-Tiering (automatically moves data based on access patterns), Standard-IA (Infrequent Access), One Zone-IA (Infrequent Access in a single AZ), Glacier Instant Retrieval (fast retrieval of archived data), Glacier Flexible Retrieval (flexible retrieval options), and Glacier Deep Archive (lowest cost, slowest retrieval). The choice depends on the frequency of data access and retrieval requirements.

4. How does AWS Lambda work and what are its use cases?

   • Answer: AWS Lambda is a serverless compute service that executes code in response to events. You upload your code (functions) and Lambda automatically manages the underlying infrastructure. It scales automatically based on demand, and you only pay for the compute time consumed. Use cases include processing data streams, responding to HTTP requests (API Gateway integration), backend logic for mobile apps, and scheduled tasks.

5. Explain the concept of Availability Zones (AZs) in AWS.

   • Answer: AZs are isolated locations within an AWS region. They are designed to be physically separated and have independent power, networking, and connectivity. Distributing resources across multiple AZs improves application availability and resilience against outages. If one AZ fails, your application can continue to operate from other AZs.

6. What are AWS IAM roles and policies?

   • Answer: AWS Identity and Access Management (IAM) roles are entities that grant permissions to AWS resources without requiring explicit credentials. IAM policies define what actions a user, role, or group can perform on AWS resources. Roles are typically used for EC2 instances or other AWS services to access other services without requiring long-term credentials, while policies control the permissions granted to those roles and users.

7. Describe the difference between RDS and DynamoDB.

   • Answer: Amazon RDS (Relational Database Service) is a managed relational database service offering various database engines (MySQL, PostgreSQL, Oracle, SQL Server, etc.). It's suitable for applications requiring structured data and ACID properties. Amazon DynamoDB is a NoSQL, key-value and document database offering scalability and high performance. It's ideal for applications needing high throughput and low latency, often for unstructured or semi-structured data.

8. How do you implement security best practices in an AWS environment?

   • Answer: Implementing robust AWS security involves several strategies: using IAM roles and policies effectively to control access, leveraging security groups and network ACLs to restrict network traffic, encrypting data at rest and in transit (using KMS), regularly patching and updating systems, monitoring security logs and events using CloudTrail and CloudWatch, implementing multi-factor authentication (MFA), and regularly performing security audits and penetration testing.

9. Explain how AWS CloudFormation works.

   • Answer: AWS CloudFormation is a service that allows you to model and provision your AWS infrastructure using declarative templates (YAML or JSON). You define the resources you need in a template, and CloudFormation creates and manages them for you. This makes it easier to automate infrastructure deployment, manage configurations, and deploy consistent environments.

10. What is AWS Auto Scaling and how does it work?

    • Answer: AWS Auto Scaling automatically adjusts the number of EC2 instances in your application based on demand. It monitors metrics (like CPU utilization or custom metrics) and scales up or down the number of instances to meet the demand, ensuring optimal performance and cost efficiency. This maintains application availability and handles traffic spikes.

11. Explain the difference between Elastic Load Balancing (ELB) and Application Load Balancing (ALB).

    • Answer: Both ELB and ALB distribute incoming traffic across multiple EC2 instances. However, ALB offers more advanced features like path-based routing, HTTP header-based routing, and support for HTTP/2 and WebSocket protocols. ELB is a more basic load balancer, suitable for simpler applications.

12. How does AWS CloudWatch work and what are its key features?

    • Answer: AWS CloudWatch is a monitoring and observability service that collects and tracks various metrics from your AWS resources and applications. Key features include monitoring EC2 instances, databases, Lambda functions, and other AWS services; creating custom dashboards to visualize metrics; setting up alarms based on thresholds; and storing and analyzing log data.

13. What are AWS Elastic Beanstalk and its benefits?

    • Answer: AWS Elastic Beanstalk is a service that simplifies deploying and managing web applications and services on AWS. It handles the underlying infrastructure, allowing developers to focus on their code. Benefits include easy deployment, automatic scaling, and simplified management of application environments.

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