1. Explain the AWS Shared Responsibility Model.
The AWS Shared Responsibility Model defines the division of security and compliance responsibilities between AWS and the customer. AWS is responsible for the security of the cloud (hardware, networking, data centers, etc.), while the customer is responsible for the security in the cloud (managing user access, data encryption, etc.).
2. How would you design a highly available and fault-tolerant web application in AWS?
To design a highly available and fault-tolerant web application, you could use Amazon EC2 instances across multiple Availability Zones to ensure redundancy. An Elastic Load Balancer (ELB) distributes incoming traffic evenly. Additionally, using Auto Scaling ensures that the application scales up or down automatically based on traffic. Implementing Amazon RDS for the database with Multi-AZ deployment would ensure high availability for your data.
3. How do you optimize cost when using AWS?
To optimize costs on AWS, consider using Reserved Instances for long-term workloads, which offer discounts in exchange for a one- or three-year commitment. Use Auto Scaling to adjust resources based on demand, ensuring you only pay for what you use. Spot Instances can also be used for non-critical workloads to save up to 90% of the cost. Regularly review your resources with AWS Trusted Advisor to identify unused or underutilized resources.
4. Describe the different types of storage options available in AWS and their use cases.
AWS provides several storage options:
- Amazon S3: Scalable object storage for data like backups and media files.
- Amazon EBS: Block storage for EC2 instances, ideal for databases or applications requiring persistent storage.
- Amazon EFS: Shared file storage for applications that require access to files across multiple EC2 instances.
- Amazon Glacier: Low-cost, archival storage for long-term data retention.
5. What are Security Groups and Network ACLs in AWS, and how do they differ?
- Security Groups: They are virtual firewalls that control inbound and outbound traffic to EC2 instances. They are stateful, meaning if you allow incoming traffic, the response is automatically allowed.
- Network ACLs: These are stateless firewalls at the subnet level that control inbound and outbound traffic for all resources in a subnet. Each rule is evaluated independently for both inbound and outbound traffic.
6. What is AWS VPC, and how would you design a secure network architecture using VPC?
An Amazon VPC (Virtual Private Cloud) allows you to create a private network within AWS. You can design a secure architecture by creating public and private subnets, where public subnets are used for resources like Load Balancers and EC2 instances that need direct internet access, and private subnets are used for databases or backend systems. Using VPN connections or Direct Connect, you can securely connect your on-premises network to the VPC.
7. What is the purpose of AWS IAM roles, and how are they different from users?
IAM roles allow you to define permissions for AWS resources and assign them to AWS services or EC2 instances. They are used to delegate access without the need for permanent credentials. IAM users are individuals or systems that interact with AWS, and each user has specific permissions. While users have long-term access, roles are temporary and used by services or EC2 instances for specific tasks.
8. How would you troubleshoot an EC2 instance that is not responding?
Start by checking the status checks in the EC2 console to determine if the instance is unhealthy. Look at CloudWatch logs to identify any application-level issues. Verify the security group and network ACL settings to ensure that network traffic is allowed. If the instance is unresponsive, try rebooting it, or if needed, create a new instance and attach the existing EBS volume to it for data recovery.
9. What is the AWS Elastic Load Balancer (ELB), and what are its different types?
AWS ELB automatically distributes incoming traffic across multiple EC2 instances to ensure high availability. There are three types of load balancers:
- Classic Load Balancer (CLB): Legacy version suitable for simple applications.
- Application Load Balancer (ALB): Best for HTTP/HTTPS traffic, providing routing based on URL paths or hostnames.
- Network Load Balancer (NLB): Best for handling high-performance, low-latency traffic such as TCP or UDP.
10. How would you migrate a large-scale on-premises database to Amazon RDS?
You can migrate an on-premises database to Amazon RDS using the AWS Database Migration Service (DMS), which allows for minimal downtime during the migration process. You would first replicate the database schema and data to RDS, then test the application with the new RDS instance. After testing, you can switch your application to use the RDS instance.
11. What are AWS Lambda functions, and how do they scale?
AWS Lambda is a serverless compute service that lets you run code without provisioning servers. Lambda automatically scales by running code in response to events, such as uploads to S3, messages in SQS, or API calls through API Gateway. It scales in real-time based on incoming traffic and stops running once the execution is complete.
12. How does Amazon S3 ensure high durability for your data?
Amazon S3 provides 99.999999999% durability for stored data by automatically replicating objects across multiple availability zones. S3 also supports versioning, so you can recover previous versions of files, and cross-region replication, which ensures that your data is replicated to other AWS regions for disaster recovery.
13. What are AWS CloudWatch and CloudTrail? How would you use them for monitoring and auditing?
- CloudWatch is a monitoring service that collects and tracks metrics, logs, and events. You can set up alarms to alert you when specific thresholds are breached, like CPU usage or memory utilization.
- CloudTrail records AWS API calls, providing a history of actions taken in your account. This is useful for auditing purposes, to monitor who accessed which resources and when.
14. How do you implement Disaster Recovery in AWS?
For disaster recovery, you can implement different strategies:
- Backup and Restore: Regularly back up your data (e.g., with Amazon S3 or EBS snapshots) and restore it in the event of a disaster.
- Pilot Light: Keep a minimal version of your application running in another region that can quickly scale up during a disaster.
- Warm Standby: Keep a scaled-down version of your app running in another region, ready to scale up when needed.
- Multi-Region Deployment: Deploy your application in multiple regions for immediate failover and minimal downtime.
15. What is AWS Auto Scaling, and how does it work?
AWS Auto Scaling automatically adjusts the number of EC2 instances based on traffic or load. It works by defining scaling policies that dictate when to add or remove instances. For example, when CPU usage exceeds 70%, Auto Scaling can add new instances, and when it drops below 30%, it can remove them.
16. How would you set up a multi-region architecture in AWS?
To set up a multi-region architecture, deploy your application in multiple regions to ensure availability and fault tolerance. You can use Amazon Route 53 to route traffic to the nearest region. For data replication, use S3 cross-region replication and RDS with Multi-Region support. You could also leverage AWS Global Accelerator to optimize traffic routing for low latency.
17. What is Amazon Route 53, and how can it be used for DNS management and load balancing?
Amazon Route 53 is a scalable Domain Name System (DNS) web service. You can use it to manage domain names and route internet traffic to your resources, such as EC2 instances, load balancers, or S3 buckets. It offers DNS failover, allowing traffic to be redirected to a healthy resource in case one becomes unavailable. It can also be used for Geo DNS to route traffic based on the user’s location.
18. How would you secure an application deployed in AWS, including network and data encryption?
To secure your application in AWS:
- Use Security Groups and Network ACLs to control traffic to your EC2 instances.
- Implement IAM roles to control access to AWS services.
- Use SSL/TLS to encrypt data in transit and Amazon KMS to encrypt data at rest in services like S3, RDS, and EBS.
- Enable AWS WAF and AWS Shield to protect against web application attacks and DDoS.
19. What is AWS Elastic Beanstalk, and how does it simplify deployment?
AWS Elastic Beanstalk is a Platform as a Service (PaaS) that allows you to deploy and manage applications without worrying about the underlying infrastructure. You simply upload your code, and Beanstalk handles the deployment, load balancing, scaling, and monitoring for you.
20. How does Amazon CloudFront work? What are its use cases?
Amazon CloudFront is a content delivery network (CDN) that distributes content globally to improve load times for users. It caches content at edge locations closer to the user, reducing latency. CloudFront is often used for serving static files (images, videos, etc.) and dynamic content, such as website APIs.
21. Describe a use case for Amazon Redshift. How would you set up a data warehouse?
Amazon Redshift is a fast, scalable data warehouse. It’s typically used for analyzing large datasets from business applications. To set it up, you create a Redshift cluster, load your data (using AWS Glue or S3), and then run SQL queries to analyze it. Redshift can integrate with BI tools like Tableau or Power BI for data visualization.
22. What is AWS SQS, and how would you use it to decouple microservices?
Amazon SQS (Simple Queue Service) is a message queue service that helps decouple microservices by allowing them to communicate asynchronously. One microservice can send a message to a queue, and another service can read the message later, improving the overall system’s scalability and resilience.
23. How would you troubleshoot a slow application hosted in AWS?
Start by checking CloudWatch metrics (like CPU, memory, and network usage) to see if resource limits are being hit. Check application logs in CloudWatch Logs for errors. Look for issues such as database bottlenecks, high latency in external APIs, or misconfigured auto-scaling. Consider using AWS X-Ray to trace application performance and identify bottlenecks in your code.
