Most Asked Interview Questions and Answers on EC2

What is Amazon EC2 and what are its primary features?

Amazon Elastic Compute Cloud (EC2) is a web service that provides resizable compute capacity in the cloud. It allows users to run virtual servers, known as instances, which can be easily scaled to meet the demands of your applications. The primary features of EC2 include:
Elasticity: Scale instances up or down as needed.
Variety of InstanceTypes: Choose instances optimized for compute, memory, storage, or GPU capabilities.
Pricing Models: On-Demand, Reserved, and Spot Instances.
Security: Leverage AWS Identity and Access Management (IAM), security groups, and network ACLs.
Flexibility: Choose your operating system and configure instances with your desired settings.

Explain the different types of EC2 instances available.

EC2 instances come in various types, each optimized for specific use cases:
General Purpose: Balanced compute, memory, and networking resources (e.g., t3, m5).
Compute Optimized: Optimized for high-performance processors (e.g., c5, c6g). Memory Optimized: Ideal for memory-intensive applications (e.g., r5, x1).
Storage Optimized: Designed for workloads requiring high, sequential read and write access to large datasets on local storage (e.g., i3, d2).
Accelerated Computing: Includes GPUs for compute-intensive tasks like machine learning and graphics processing (e.g., p3, g4).

What are EC2 pricing models and how do they differ?

EC2 offers several pricing models:
On-Demand: Pay for compute capacity by the hour or second with no long-term commitments.
Reserved Instances: Commit to a one or three-year term to receive a significant discount.
Spot Instances: Purchase unused EC2 capacity at a reduced rate, but these instances can be terminated by AWS when the capacity is needed elsewhere. Savings Plans: Flexible pricing model offering lower prices in exchange for a commitment to a consistent amount of usage over a period.
Dedicated Hosts: Physical servers dedicated for your use, allowing you to use existing server-bound software licenses.

How can you secure your EC2 instances?

Securing EC2 instances involves: Using Security Groups: Acts as a virtual firewall, and controlling inbound and outbound traffic to instances.
Network ACLs: Provides an additional layer of security at the subnet level within a VPC.
SSH Key Pairs: Used to securely access instances.
IAM Roles: Assign roles to instances to control access to AWS services and resources.
Encryption: Encrypt EBS volumes and data stored on the instance.
Regular Patching: Keep your instances updated with the latest security patches.

What are the different types of storage options available for EC2?

EC2 instances can utilize several types of storage options:
Amazon Elastic Block Store (EBS): Persistent block-level storage volumes that can be attached to EC2 instances.
Instance Store: Ephemeral storage that provides temporary block-level storage for instances.
Amazon Elastic File System (EFS): Fully managed file storage that can be mounted on EC2 instances.
Amazon S3: Object storage suitable for storing and retrieving any amount of data from anywhere on the web.

What is an EC2 instance lifecycle, and what are the key states?

An EC2 instance goes through several states during its lifecycle:
Pending: The instance is being prepared to launch.
Running: The instance is currently running and ready for use.
Stopping: The instance is in the process of being stopped.
Stopped: The instance is stopped and not running, but can be restarted.
Shutting Down: The instance is in the process of being terminated.
Terminated: The instance has been permanently deleted and cannot be restarted.

How do you monitor and troubleshoot an EC2 instance?

Monitoring and troubleshooting EC2 instances can be done using:
Amazon CloudWatch: Provides metrics and logs for monitoring instance performance and activity.
EC2 Instance Status Checks: Automatically monitors the health of instances and underlying hardware.
VPC Flow Logs: Capture and analyze traffic flowing to and from your instances. Enhanced Networking: Use ENA or Intel 82599 VF interface for better network performance.
Logs: Review application and system logs stored on the instance or sent to CloudWatch.

What is an AMI and how does it relate to EC2?

An Amazon Machine Image (AMI) is a template that contains the software configuration (OS, application server, and applications) required to launch an EC2 instance. When you launch an instance, you specify an AMI, and the instance is created using the configurations in that AMI. Custom AMIs can be created by users for specific configurations, ensuring consistency across instances.

What are EC2 Placement Groups and their types?

Placement Groups are a way to influence the placement of your instances on the underlying hardware:
Cluster Placement Group: Places instances close together within a single Availability Zone for high-bandwidth, low-latency networking.
Spread Placement Group: Distributes instances across different hardware to reduce the risk of simultaneous failures.
Partition Placement Group: Divides instances into logical partitions, each placed on different racks, minimizing the impact of hardware failure on your instances.

What is Auto Scaling and how does it work with EC2?

Auto Scaling ensures that you have the right number of EC2 instances available to handle the load of your application. It works by:
Scaling Out: Adding instances when demand increases.
Scaling In: Removing instances when demand decreases.
Scheduled Scaling: Based on time or predictable load patterns.
Dynamic Scaling: Based on demand metrics such as CPU utilization or other custom metrics.
Auto Scaling Groups: Group of EC2 instances managed together, where scaling policies are defined to automatically adjust the capacity.

Companies Where These Questions Are Frequently Asked

Amazon Web Services (AWS), Microsoft, Google, IBM, Accenture, Deloitte, Capgemini, Cognizant, JP Morgan Chase, Netflix.