Question 1

What is AWS, and what is the difference between Regions and Availability Zones (AZs)?

Accepted Answer

AWS (Amazon Web Services) is a comprehensive cloud computing platform. An AWS Region is a geographical area (like us-east-1) containing multiple data center clusters. An Availability Zone (AZ) is one or more discrete data centers with redundant power, networking, and connectivity within an AWS Region. High availability is achieved by deploying applications across multiple AZs.

Question 2

What is Amazon EC2, and what are its different instance pricing models?

Accepted Answer

Amazon EC2 (Elastic Compute Cloud) provides secure, resizable compute capacity in the cloud. Pricing models include:
1. On-Demand: Pay by the second/hour, no commitment. Best for short-term, unpredictable workloads.
2. Reserved Instances (RIs): Commit to 1-3 years for up to 72% discount. Best for steady-state workloads.
3. Savings Plans: Commit to hourly spend for discounts across EC2/Fargate/Lambda.
4. Spot Instances: Bid on spare AWS capacity for up to 90% discount. Can be terminated by AWS with 2 min warning. Best for fault-tolerant, batch jobs.

Question 3

What is Amazon S3, and what are its storage classes?

Accepted Answer

Amazon S3 (Simple Storage Service) is an object storage service offering industry-leading scalability and durability. Storage classes include:
1. S3 Standard: For active, frequently accessed data.
2. S3 Intelligent-Tiering: Automatically moves data to cost-optimal tier based on access patterns.
3. S3 Standard-IA: For infrequently accessed data that requires rapid access.
4. S3 One Zone-IA: Lower cost IA stored in a single AZ (less resilient).
5. S3 Glacier (Instant, Flexible, Deep Archive): Low-cost archiving, retrieval times range from minutes to 12 hours.

Question 4

What is AWS IAM, and what are its core components?

Accepted Answer

AWS IAM (Identity and Access Management) enables secure access to AWS resources. Core components:
1. Users: Individuals representing a person or service account.
2. Groups: Collections of IAM users with shared permissions.
3. Roles: Identifiers with policies that can be assumed by users, applications, or AWS services (like EC2 instances).
4. Policies: JSON documents defining allowed or denied actions on specific resources.

Question 5

Explain the difference between a Security Group and a Network Access Control List (NACL).

Accepted Answer

Security Groups act as a firewall at the *instance level*. They are stateful (inbound allowed traffic is automatically allowed outbound) and support 'allow' rules only. NACLs act as a firewall at the *subnet level*. They are stateless (inbound and outbound rules must be defined explicitly), support both 'allow' and 'deny' rules, and process rules in numerical order.

Question 6

What is an Application Load Balancer (ALB) vs a Network Load Balancer (NLB)?

Accepted Answer

An ALB operates at Layer 7 (Application) of the OSI model. It supports routing based on content paths, hostnames, and HTTP headers, making it ideal for web applications and microservices. An NLB operates at Layer 4 (Transport), handles millions of requests per second with ultra-low latency, and maps static IPs. Best for high-performance TCP/UDP workloads.

Question 7

What is serverless computing, and how does AWS Lambda work?

Accepted Answer

Serverless computing allows running applications without provisioning or managing servers. AWS Lambda is an event-driven serverless compute service that runs code in response to events (API requests, S3 uploads, DynamoDB updates). You only pay for the compute time consumed (measured in milliseconds).

Question 8

What is Amazon VPC?

Accepted Answer

Amazon VPC (Virtual Private Cloud) lets you provision a logically isolated section of the AWS cloud where you can launch AWS resources in a virtual network you define. You have complete control over subnets, IP address ranges, routing tables, and network gateways.

Question 9

What is the difference between Public Subnets and Private Subnets in a VPC?

Accepted Answer

A Public Subnet has a route in its routing table pointing to an **Internet Gateway (IGW)**, allowing instances to communicate directly with the internet and have public IPs. A Private Subnet does not have a direct route to the internet. To access the internet (e.g. for updates), instances in a private subnet route outbound traffic through a **NAT Gateway** located in a public subnet.

Question 10

What is AWS Auto Scaling?

Accepted Answer

AWS Auto Scaling monitors your applications and automatically adjusts capacity (adds or removes EC2 instances, ECS tasks, etc.) to maintain steady, predictable performance at the lowest possible cost, responding to metrics like CPU load or network traffic.

Question 11

What is Amazon RDS, and how does it support high availability?

Accepted Answer

Amazon RDS (Relational Database Service) makes it easy to set up, operate, and scale relational databases in the cloud. High availability is achieved using **Multi-AZ deployments**, where RDS automatically replicates data synchronously to a standby database instance in a different Availability Zone. In case of primary failure, RDS fails over automatically.

Question 12

What is Amazon DynamoDB?

Accepted Answer

Amazon DynamoDB is a fully managed, serverless, key-value NoSQL database service designed to deliver single-digit millisecond performance at any scale. It supports document models, automatic partitioning, scaling, and global tables for multi-region replication.

Question 13

Explain the purpose of Amazon Route 53.

Accepted Answer

Amazon Route 53 is a highly available and scalable Domain Name System (DNS) web service. It translates human-friendly domain names (like example.com) into numeric IP addresses, registers new domain names, and supports routing policies (failover, latency, geolocation, weighted routing).

Question 14

What is AWS CloudFront?

Accepted Answer

AWS CloudFront is a fast content delivery network (CDN) service that securely delivers data, videos, applications, and APIs to users globally with low latency and high transfer speeds, caching static and dynamic content at edge locations worldwide.

Question 15

What is the difference between AWS CloudTrail and Amazon CloudWatch?

Accepted Answer

CloudWatch monitors the performance, health, and logs of your AWS resources and applications (CPU usage, database storage, custom log streams). CloudTrail records API calls and actions made within your AWS account (who accessed what, when, and from where), serving as an audit log.

Question 16

What is the AWS Shared Responsibility Model?

Accepted Answer

The Shared Responsibility Model defines security boundaries. AWS is responsible for security *of* the cloud (infrastructure, physical security of data centers, hardware, virtualization layer). The Customer is responsible for security *in* the cloud (customer data, operating system updates, network access rules, identity access privileges, encryption).

Question 17

What is Infrastructure as Code (IaC), and how is it used in AWS?

Accepted Answer

IaC is the practice of managing and provisioning infrastructure using machine-readable configuration files instead of manual GUI setups. In AWS, this is done using **AWS CloudFormation** (templates written in JSON/YAML) or the **AWS CDK** (Cloud Development Kit, using TS, Python, Java) to automate resource deployments.

Question 18

What is a Cold Start in AWS Lambda, and how do you reduce it?

Accepted Answer

A Cold Start occurs when a Lambda function is invoked after being idle, requiring AWS to spin up a new container container instance and initialize runtime/code. Ways to reduce it include: keeping deployment bundles small, choosing fast runtimes (Go, Node.js over Java/C#), or enabling **Provisioned Concurrency** to keep containers warm.

Question 19

Explain the difference between SQS and SNS.

Accepted Answer

SQS (Simple Queue Service) is a message queuing service used to decouple microservices. It works on a **pull-model** (receivers poll and delete messages from queue). SNS (Simple Notification Service) is a pub-sub messaging service working on a **push-model** (pushes messages to all subscribed endpoints, like Lambda, SQS, email, SMS).

Question 20

How do you securely connect an on-premise network to an AWS VPC?

Accepted Answer

Secure connections can be achieved via:
1. **AWS Site-to-Site VPN**: Sets up an IPsec VPN connection over the public internet. Cost-effective and quick to set up.
2. **AWS Direct Connect**: Bypasses the internet, establishing a dedicated, private physical network connection from the customer's data center to AWS. Best for high bandwidth, low latency, and consistent throughput.

AWS Cloud Interview Master

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What is AWS, and what is the difference between Regions and Availability Zones (AZs)?

What is Amazon EC2, and what are its different instance pricing models?

What is Amazon S3, and what are its storage classes?

What is AWS IAM, and what are its core components?

Explain the difference between a Security Group and a Network Access Control List (NACL).

What is an Application Load Balancer (ALB) vs a Network Load Balancer (NLB)?

What is serverless computing, and how does AWS Lambda work?

What is Amazon VPC?

What is the difference between Public Subnets and Private Subnets in a VPC?

What is AWS Auto Scaling?

What is Amazon RDS, and how does it support high availability?

What is Amazon DynamoDB?

Explain the purpose of Amazon Route 53.

What is AWS CloudFront?

What is the difference between AWS CloudTrail and Amazon CloudWatch?

What is the AWS Shared Responsibility Model?

What is Infrastructure as Code (IaC), and how is it used in AWS?

What is a Cold Start in AWS Lambda, and how do you reduce it?

Explain the difference between SQS and SNS.

How do you securely connect an on-premise network to an AWS VPC?

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