AWS Cloud Fundamentals

## What Is Cloud Computing? Cloud computing delivers computing resources — servers, storage, databases, networking, and software — over the internet on a pay-as-you-go model. Instead of buying and maintaining physical hardware, you rent what you need and scale up or down as demand changes. AWS (Amazon Web Services) is the largest cloud provider, offering over 200 services. This guide covers the foundational services you will use most often. ## Setting Up Your AWS Account ```bash # Install the AWS CLI pip install awscli # Configure credentials aws configure # Enter your Access Key ID, Secret Access Key, region, and output format # Verify setup aws sts get-caller-identity ``` Store credentials securely using environment variables or the `~/.aws/credentials` file. Never commit secrets to **GitHub**. ## EC2: Virtual Servers EC2 (Elastic Compute Cloud) provides resizable virtual machines in the cloud. ### Launching an Instance ```bash # Launch a t3.micro instance (free tier eligible) aws ec2 run-instances \ --image-id ami-0c55b159cbfafe1f0 \ --instance-type t3.micro \ --key-name my-key-pair \ --security-group-ids sg-0123456789abcdef0 \ --subnet-id subnet-0123456789abcdef0 \ --tag-specifications 'ResourceType=instance,Tags=[{Key=Name,Value=MyServer}]' ``` ### Managing Instances ```bash # List running instances aws ec2 describe-instances --filters "Name=instance-state-name,Values=running" # Stop an instance aws ec2 stop-instances --instance-ids i-0123456789abcdef0 # Terminate an instance aws ec2 terminate-instances --instance-ids i-0123456789abcdef0 ``` ### Key Concepts - **AMI**: Amazon Machine Image — the OS template for your instance. - **Instance Type**: Determines CPU, memory, and network capacity. - **Security Group**: Virtual firewall controlling inbound and outbound traffic. - **Key Pair**: SSH credentials for accessing Linux instances. ## S3: Object Storage S3 (Simple Storage Service) stores any amount of data with high durability (99.999999999%). ### Creating and Using Buckets ```bash # Create a bucket aws s3 mb s3://my-unique-bucket-name-2026 # Upload a file aws s3 cp ./local-file.txt s3://my-unique-bucket-name-2026/documents/file.txt # Upload an entire directory aws s3 cp ./build/ s3://my-unique-bucket-name-2026/assets/ --recursive # List bucket contents aws s3 ls s3://my-unique-bucket-name-2026/ # Download a file aws s3 cp s3://my-unique-bucket-name-2026/documents/file.txt ./downloaded-file.txt ``` ### Static Website Hosting ```bash # Enable website hosting aws s3 website s3://my-unique-bucket-name-2026 \ --index-document index.html \ --error-document error.html # Set a bucket policy for public read access aws s3api put-bucket-policy \ --bucket my-unique-bucket-name-2026 \ --policy file://policy.json ``` This pattern is useful for hosting static sites deployed from **Vercel** or CI/CD pipelines. ## Lambda: Serverless Functions Lambda runs code without provisioning or managing servers. You pay only for the compute time consumed. ### Your First Lambda Function ```javascript // index.mjs export const handler = async (event) => { const name = event.queryStringParameters?.name || "World"; return { statusCode: 200, headers: { "Content-Type": "application/json" }, body: JSON.stringify({ message: `Hello, ${name}!`, timestamp: new Date().toISOString(), }), }; }; ``` ```bash # Package and deploy zip function.zip index.mjs aws lambda create-function \ --function-name hello-world \ --runtime nodejs20.x \ --role arn:aws:iam::123456789012:role/lambda-role \ --handler index.handler \ --zip-file fileb://function.zip # Test the function aws lambda invoke --function-name hello-world \ --payload '{"queryStringParameters":{"name":"DevAtlas"}}' \ output.json cat output.json ``` ### Lambda with API Gateway Lambda functions are often exposed via API Gateway for HTTP access: ```yaml # SAM template snippet Resources: HelloFunction: Type: AWS::Serverless::Function Properties: Runtime: nodejs20.x Handler: index.handler Events: Hello: Type: Api Properties: Path: /hello Method: get ``` ## IAM: Identity and Access Management IAM controls who can access what. Follow the principle of least privilege. ```bash # Create a read-only user aws iam create-user --user-name readonly-user aws iam create-access-key --user-name readonly-user # Attach a managed policy aws iam attach-user-policy \ --user-name readonly-user \ --policy-arn arn:aws:iam::aws:policy/ReadOnlyAccess ``` ### Best Practices - Never use the root account for daily operations. - Create IAM users and groups for team members. - Use roles for applications and services, not long-lived credentials. - Enable MFA on all privileged accounts. ## RDS: Managed Databases RDS (Relational Database Service) manages PostgreSQL, MySQL, and other databases with automated backups and scaling. ```bash # Create a PostgreSQL instance aws rds create-db-instance \ --db-instance-identifier mydb \ --db-instance-class db.t3.micro \ --engine postgres \ --master-username admin \ --master-user-password YourSecurePassword123 \ --allocated-storage 20 \ --backup-retention-period 7 \ --multi-az ``` ## Cost Optimization - Use **EC2 Spot Instances** for fault-tolerant workloads (up to 90% savings). - Enable **S3 Intelligent-Tiering** for data with unpredictable access patterns. - Set up **AWS Budgets** and **Cost Explorer** alerts to avoid surprises. - Use the **Free Tier** for learning and prototyping. ## Architecting a Simple Web Application A common architecture for beginners combines these services: ``` User → Route 53 (DNS) → CloudFront (CDN) → S3 (Static Frontend) ↘ API Gateway → Lambda (API) → DynamoDB (Database) ``` This serverless pattern eliminates server management entirely, scales automatically, and minimizes cost at low traffic levels. ## Next Steps Once you are comfortable with these core services, explore **DynamoDB** for serverless NoSQL, **SQS** and **SNS** for messaging, **ECS** and **EKS** for container orchestration, and **CloudFormation** for infrastructure as code. Consider deploying your applications with **Vercel** or a CI/CD pipeline hosted on **GitHub** Actions.