FAQ's: AWS EC2 Service

1. What is Amazon EC2?

Amazon Elastic Compute Cloud (EC2) is a web service that provides resizable compute capacity in the cloud. It is designed to make web-scale cloud computing easier for developers.

2. What are the different types of EC2 instances?

EC2 instances are categorized into different families based on their intended use case. The main categories are

1. 1 .      General Purpose (e.g., t3, t3a, m5, m5a),
2.    Compute Optimized (e.g., c5, c5n),
3.    Memory Optimized (e.g., r5, r5a),
4.   Storage Optimized (e.g., i3, d2), and
5.   Accelerated Computing (e.g., p3, g4).

3. What is the difference between stopping and terminating an EC2 instance?

When you stop an instance, it shuts down and you can restart it later, preserving all data on the instance store and EBS volumes. When you terminate an instance, it is permanently deleted, and you lose all data stored on the instance store. EBS volumes can be retained depending on their settings.

Intermediate Questions

4. How do you resize an EC2 instance?

To resize an EC2 instance, you need to:

o   Stop the instance.

o   Change the instance type from the EC2 console or using the AWS CLI.

o   Start the instance again.

5. What is an AMI and how is it used?

An Amazon Machine Image (AMI) provides the information required to launch an instance. It includes a template for the root volume of the instance (an operating system, application server, and applications), launch permissions, and a block device mapping specifying the volumes to attach to the instance when it's launched.

6. Explain the concept of Elastic IP addresses.

An Elastic IP address is a static IPv4 address designed for dynamic cloud computing. It allows you to mask the failure of an instance or software by rapidly remapping the address to another instance in your account.

7. How do you secure data on your EC2 instances?

Data security on EC2 instances can be achieved through:

• Using security groups and network ACLs to control inbound and outbound traffic.
• Encrypting data at rest using EBS encryption and at transit using protocols such as HTTPS and SSH.
• Implementing IAM roles and policies to manage access permissions.
• Regularly updating and patching the operating system and applications.

 

Advanced Questions

8. What is the difference between EBS-backed and instance store-backed instances?

EBS-backed instances use Elastic Block Store (EBS) volumes as their root device, allowing data to persist independently from the life of the instance. Instance store-backed instances use temporary storage located on disks that are physically attached to the host computer. Data on instance store volumes is lost when the instance is stopped or terminated.

9. How do you optimize the performance of an EC2 instance?

Performance optimization can be done through:

• Choosing the appropriate instance type and size based on the workload.
• Using EBS-optimized instances for high I/O performance.
• Distributing the workload using Auto Scaling and Elastic Load Balancing.
• Utilizing Placement Groups for low-latency and high-throughput networking.
• Configuring instance storage for optimal I/O performance (e.g., RAID configurations).

10. Explain the concept of Spot Instances and their use cases.

Spot Instances allow you to bid on spare Amazon EC2 computing capacity at reduced rates compared to On-Demand pricing. They are ideal for flexible, fault-tolerant, and stateless applications such as big data analysis, batch processing, CI/CD, and web services. Spot Instances can be interrupted by AWS when there is higher demand for EC2 capacity, but they can offer significant cost savings.

11. Describe how you would implement high availability and fault tolerance for an application running on EC2.

High availability and fault tolerance can be achieved through: - Distributing instances across multiple Availability Zones (AZs). - Using Elastic Load Balancers (ELBs) to distribute traffic evenly across instances. - Implementing Auto Scaling to automatically replace unhealthy instances and scale capacity based on demand. - Using Multi-AZ deployments for databases and other critical components. - Regularly backing up data and implementing disaster recovery plans.

Scenario-Based Questions

12. How would you migrate an on-premises application to AWS EC2?

Migrating an on-premises application to AWS EC2 involves:

a)     Assessing the current environment and defining requirements.

b)     Selecting the appropriate EC2 instance types.

c)     Creating AMIs from the on-premises servers or installing the application on new EC2 instances.

d)     Configuring networking (VPC, subnets, security groups).

e)     Migrating data using tools like AWS Database Migration Service (DMS), AWS Snowball, or direct data transfer.

f)       Testing the application in the AWS environment.

g)     Switching over DNS and updating any necessary configurations.

13. How do you monitor and troubleshoot performance issues on EC2 instances?

Monitoring and troubleshooting performance issues can be done using:

o   Amazon CloudWatch to monitor metrics such as CPU, memory, disk I/O, and network traffic.

o   AWS CloudTrail for auditing API calls.

o   VPC Flow Logs for monitoring network traffic.

o   EC2 instance logs and application logs.

o   Diagnosing performance bottlenecks through AWS X-Ray for distributed applications.

o   Using tools like htop, iostat, and netstat for real-time monitoring on the instance itself.

14. Explain the process of setting up a VPC for your EC2 instances

Setting up a VPC involves:

a)     Creating a VPC with a specified CIDR block.

b)     Adding subnets in different Availability Zones.

c)     Configuring route tables for internal and external traffic.

d)     Creating and associating Internet Gateways for public subnets.

e)     Setting up NAT Gateways or instances for private subnets.

f)       Configuring security groups and network ACLs to control traffic.

g)     Optionally, setting up VPC peering, VPN connections, or Direct Connect for hybrid cloud setups.

Additional Questions

15. What are the best practices for managing AWS EC2 costs?

Best practices for managing EC2 costs include:

o   Using AWS Cost Explorer and budgets to monitor and set alerts for usage.

o   Right-sizing instances to match the workload.

o   Using Reserved Instances or Savings Plans for long-term workloads.

o   Leveraging Spot Instances for non-critical workloads.

o   Automating start/stop schedules for non-production environments.

o   Using AWS Trusted Advisor for cost optimization recommendations.

16. How would you handle a situation where your EC2 instances are running but your application is not reachable?

Troubleshooting steps include:

o   Checking the instance status and system logs

o   Verifying security group and network ACL rules to ensure they allow the necessary traffic.

o   Ensuring the correct route tables and subnets are configured.

o   Checking the application logs for errors.

o   Verifying that the application services are running.

o   Testing network connectivity to the instance.