AWS EC2 Interview Questions: Mastering Cloud Computing

Amazon Elastic Compute Cloud (EC2) is a core service offered by Amazon Web Services (AWS) that provides resizable, scalable compute capacity in the cloud. It is designed to simplify cloud computing by enabling users to quickly deploy and manage virtual servers without the need for physical hardware.

1. What is Amazon EC2?

Amazon EC2 is a web service that provides secure, resizable compute capacity in the cloud. It allows you to run virtual servers (called instances) on demand, offering full control over the computing resources and the ability to scale up or down as needed.

• Scalability: Scale instances up or down to match workload requirements.
• Flexibility: Wide range of instance types optimized for different use cases.
• Cost-Efficiency: Pay only for the compute capacity used, with options like Reserved and Spot Instances for cost savings.
• Security: Control access to instances through security groups, VPC, and IAM roles.

2. Key Concepts in Amazon EC2

a. Instances

An EC2 instance is a virtual server running on AWS. You can choose different instance types based on your application’s needs, such as compute, memory, or storage-optimized instances.

b. Amazon Machine Images (AMIs)

An AMI is a template that contains the OS, software, configurations, and application code needed to launch an instance.

c. Instance Types

• General Purpose: t3, m6g (Balanced CPU, memory, and networking).
• Compute Optimized: c7g (CPU-intensive applications).
• Memory Optimized: r7a (High memory workloads like databases).
• Storage Optimized: i4i (High disk I/O workloads).
• Accelerated Computing: p5, inf1 (Machine learning and graphics processing).

d. Elastic Block Store (EBS)

EBS provides persistent block storage for EC2 instances.

e. Elastic IP Addresses

An Elastic IP (EIP) is a static, public IP address that you can allocate and assign to an instance.

f. Security Groups

Security Groups act as virtual firewalls to control inbound and outbound traffic.

3. EC2 Instance Lifecycle

• Pending: The instance is being launched.
• Running: The instance is up and running.
• Stopping/Stopped: The instance is shutting down but data on EBS volumes remains.
• Terminated: The instance has been permanently deleted.

4. Launching an EC2 Instance

The process involves choosing an AMI, selecting an instance type, configuring details, adding storage, setting up security groups, and launching.

5. Use Cases for Amazon EC2

• Web Hosting: Running scalable web applications and APIs.
• Data Processing: Batch processing, big data analysis, and ETL.
• Machine Learning & AI: Training models and running inferencing jobs.
• DevOps & CI/CD: Continuous integration and delivery pipelines.
• High-Performance Computing: Scientific simulations and data-intensive workloads.

6. Benefits of Using Amazon EC2

• Elastic Scalability: Automatically scale resources.
• Global Reach: Deploy in multiple AWS regions.
• Cost Savings: Flexible pricing models.
• Security & Compliance: Built-in security with industry compliance.
• Ease of Use: Simple tools like AWS CLI, SDKs, and CloudFormation.

• Q1.What is Amazon EC2? Amazon Elastic Compute Cloud (EC2) is a web service that provides scalable, resizable compute capacity in the cloud. It allows users to launch virtual servers on demand with customizable hardware, operating systems, and configurations.
• What are the different types of EC2 instances? EC2 offers various instance types optimized for specific use cases:
  • General Purpose: t3, t4g, m6g (balanced resources).
  • Compute Optimized: c7g, c5 (CPU-heavy workloads).
  • Memory Optimized: r7a, x2gd (memory-intensive applications).
  • Storage Optimized: i4i, d3 (high disk I/O).
  • Accelerated Computing: p5, inf1 (machine learning, GPU).
• Explain the EC2 pricing models.
  • On-Demand Instances: Pay per hour or second with no upfront commitment.
  • Reserved Instances: Pay upfront to reserve capacity for 1 to 3 years with significant discounts.
  • Spot Instances: Purchase unused capacity at a reduced rate; suitable for flexible workloads.
  • Savings Plans: Commit to a consistent usage level for cost savings.
  • Dedicated Hosts/Instances: Physical servers for compliance and licensing needs.
• What is an AMI (Amazon Machine Image)? An AMI is a pre-configured template containing an OS, application server, and software to quickly launch EC2 instances. It serves as a blueprint for deploying instances.
• What is an Elastic IP Address? An Elastic IP (EIP) is a static public IP address that you can allocate to an EC2 instance. It allows you to mask the failure of an instance by quickly remapping the IP to a different instance.
• What are Security Groups in EC2? Security Groups act as virtual firewalls for controlling inbound and outbound traffic to your instances. You can define rules based on IP address ranges, protocols, and port numbers.
• Explain the EC2 Instance Lifecycle. An EC2 instance can go through the following states:
  • Pending: The instance is being launched.
  • Running: The instance is active.
  • Stopping/Stopped: The instance is being shut down or stopped, but data on EBS volumes persists.
  • Terminated: The instance is permanently deleted, and associated data is lost unless backed up.
• How do you launch an EC2 instance? Steps to launch an EC2 instance:
  • Choose an AMI.
  • Select an instance type.
  • Configure instance details (network, IAM roles).
  • Add storage (EBS volumes).
  • Configure security groups.
  • Review and launch the instance.
• What is Amazon EBS (Elastic Block Store)? Amazon EBS provides persistent block storage for EC2 instances. EBS volumes can be attached or detached from instances and support snapshots for backups.
• How can you monitor EC2 instances? You can use Amazon CloudWatch to monitor CPU utilization, disk I/O, network traffic, and memory usage. CloudWatch alarms can notify you of instance performance issues.
• What is the difference between stopping and terminating an EC2 instance?
  • Stopping: The instance is powered off, but the EBS volume remains intact. You are not charged for the instance while stopped.
  • Terminating: The instance and attached EBS volumes are deleted (unless specified otherwise).
• What are the benefits of using Auto Scaling with EC2? Auto Scaling allows automatic scaling of EC2 instances based on defined metrics. It helps:
  • Optimize cost by adjusting capacity according to demand.
  • Maintain availability by replacing unhealthy instances.
  • Handle sudden traffic spikes efficiently.
• How do Spot Instances work? Spot Instances let you bid for unused EC2 capacity at a lower cost. However, they can be terminated by AWS if capacity is needed for On-Demand Instances. They're ideal for non-critical or batch processing tasks.
• How do you secure access to your EC2 instances? Use IAM roles to control permissions. Apply Security Groups and Network ACLs for network traffic. Utilize SSH key pairs for Linux instances and RDP for Windows instances. Implement VPC configurations for network isolation.
• What is the use of EC2 Placement Groups?
  • Cluster: Instances in a low-latency group within a single Availability Zone.
  • Partition: Instances spread across logical partitions for distributed workloads.
  • Spread: Instances placed on distinct hardware for fault tolerance.
• Explain Elastic Load Balancing with EC2. Elastic Load Balancing (ELB) distributes incoming traffic across multiple EC2 instances to improve fault tolerance, scalability, and availability.
• What is the difference between an Instance Store and EBS-backed volumes?
  • Instance Store: Temporary storage that is lost if the instance is stopped or terminated.
  • EBS-backed: Persistent storage that retains data even when the instance is stopped or terminated.
• How can you back up your EC2 instances? Use EBS Snapshots to create backups of EBS volumes. You can automate snapshots with AWS Backup or Lambda functions.
• What are the common EC2 instance purchasing options for cost optimization? Use Reserved Instances for predictable workloads. Take advantage of Spot Instances for cost-efficient batch jobs. Use Savings Plans for flexible long-term cost savings.
• What is the difference between Public IP and Elastic IP?
  • Public IP: Assigned automatically and changes when the instance is stopped/restarted.
  • Elastic IP: Static IP that remains the same even when the instance is stopped or restarted.