☁️ Day 30: AWS S3 & Lambda — Object Storage + Serverless Automation

Today’s deep dive covers two fundamental AWS services:

• Amazon S3: Scalable object storage for static files, backups, and web hosting.

• AWS Lambda: Serverless compute service that executes code on-demand without provisioning servers.

We also showcase a real-world project where a personal portfolio website is hosted on S3, and explore how Lambda functions can be triggered by S3 events, e.g., for automation on file upload.

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🧠 Theory: What Is Amazon S3?

Amazon Simple Storage Service (S3) is:

• A durable, highly scalable object storage system.

• Used to store files like images, videos, HTML, JSON, CSV, backups, etc.

• Common for:

  • Hosting static websites

  • Media content delivery

  • Data lake storage

  • Backup and restore

  • Triggering serverless actions

Each object is stored in a bucket and identified by a key (file path).

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🧠 Theory: What Is AWS Lambda?

AWS Lambda is a serverless compute service that:

• Runs your code in response to triggers/events

• Supports languages like Python, Node.js, Java, Go, etc.

• No server management

• You only pay for execution time

• Common triggers:

  • S3 (file upload)

  • API Gateway

  • DynamoDB Streams

  • CloudWatch Events

  • SNS/SQS

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🔧 AWS S3 Setup – Step-by-Step (Static Website Hosting)

✅ Step 1: Create S3 Bucket

aws s3 mb s3://my-portfolio-website

✅ Step 2: Enable Static Website Hosting

From AWS Console → S3 → Your Bucket → Properties
Enable “Static Website Hosting”

• Index document: index.html

• Error document: error.html (optional)

✅ Step 3: Set Bucket Policy for Public Read

{
  "Version": "2012-10-17",
  "Statement": [{
    "Sid": "PublicReadGetObject",
    "Effect": "Allow",
    "Principal": "*",
    "Action": "s3:GetObject",
    "Resource": "arn:aws:s3:::my-portfolio-website/*"
  }]
}

Apply this in the Permissions → Bucket Policy section.

✅ Step 4: Upload Files

aws s3 sync ./portfolio-website s3://my-portfolio-website

Your site is now live at:

http://my-portfolio-website.s3-website-<region>.amazonaws.com

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✨ Project Highlight: 🚀 Personal Portfolio Hosted on S3

📌 What You Built:

A responsive one-page portfolio featuring:

• About

• Skills

• Projects

• Contact section

🧱 Folder Structure:

portfolio-website/
├── index.html
├── style.css
├── images/
└── scripts/

🌐 Hosted at:

http://your-bucket-name.s3-website-region.amazonaws.com

No server needed. No EC2. Just fast, scalable S3.

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🔁 AWS Lambda Triggered by S3 Upload

🎯 Goal:

Trigger a Lambda function when a new file is uploaded to a specific S3 bucket.

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🪜 Setup: Lambda + S3 Trigger (Python Example)

✅ Step 1: Create Lambda Function

From AWS Console → Lambda → Create function

• Runtime: Python 3.9

• Permissions: Create new role with basic Lambda permissions

Function code (example):

import json

def lambda_handler(event, context):
    for record in event['Records']:
        bucket = record['s3']['bucket']['name']
        key = record['s3']['object']['key']
        print(f"File uploaded: s3://{bucket}/{key}")
    return {
        'statusCode': 200,
        'body': json.dumps('Success')
    }

✅ Step 2: Add Trigger from S3

From Lambda Console:

• Add trigger → Choose S3

• Choose your S3 bucket

• Event type: PUT (Object created)

• Prefix (optional): e.g., uploads/

• Suffix (optional): e.g., .jpg

Grant S3 permission to invoke Lambda.

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📦 Use Case Examples

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🧪 Sample CLI Commands

Create S3 Bucket

aws s3 mb s3://trigger-demo-bucket

Upload a Test File

aws s3 cp test.txt s3://trigger-demo-bucket/uploads/

Lambda will be triggered automatically.

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🛡️ Best Practices

• Enable versioning in S3

• Use S3 Lifecycle Policies for auto-deletion

• Use environment variables in Lambda

• Use CloudWatch for monitoring Lambda execution

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📘 Summary

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🔮 What’s Next?

🔮 What’s Next? – Day 31 Preview
Tomorrow’s learning lineup is all about powerful AWS services that handle data, routing, and app deployment:

🔧 AWS CLI – Automate and control your AWS services using command-line tools

🗃️ DynamoDB – Explore AWS's fully managed NoSQL database
✔️ Fast, scalable, and serverless
✔️ Ideal for key-value and document-based workloads

🌐 Route 53 – AWS's highly available DNS service
✔️ Route traffic globally
✔️ Register custom domains and apply routing policies

🚀 Elastic Beanstalk – Simplified app deployment
✔️ Deploy web apps without worrying about infrastructure
✔️ Automatically handles provisioning, load balancing, and scaling

Stay tuned for hands-on setups, real use cases, and clear breakdowns!