AWS Core Services Overview

Why AWS?

AWS launched in 2006 and has ~32% of the cloud market. Most job descriptions mention AWS. Most startups run on AWS. Understanding the core services is essential for any backend or DevOps engineer.

The good news: you don't need to know all 200+ services. 90% of applications use fewer than 15.

The AWS Service Map

Compute

EC2 — Elastic Compute Cloud

Virtual machines in the cloud. The most fundamental AWS service.

# Launch a server in 60 seconds
aws ec2 run-instances \
  --image-id ami-0abcdef1234567890 \
  --instance-type t3.micro \
  --key-name my-key-pair

• Choose from 400+ instance types (CPU, memory, GPU optimized)
• Pay by the second
• t3.micro is free tier eligible — good for learning

Lambda — Serverless Functions

Run code without managing servers. Pay only when code runs.

// Lambda function — runs on demand, scales automatically
export const handler = async (event) => {
  const name = event.queryStringParameters?.name ?? "World";
  return {
    statusCode: 200,
    body: JSON.stringify({ message: `Hello, ${name}!` }),
  };
};

• Scales from 0 to thousands of concurrent executions automatically
• Free tier: 1 million requests/month
• Max execution time: 15 minutes

ECS — Elastic Container Service

Run Docker containers at scale. Managed container orchestration.

Storage

S3 — Simple Storage Service

Object storage for any file type. Infinitely scalable.

// Upload a file to S3
const s3 = new S3Client({ region: "ap-south-1" });
await s3.send(new PutObjectCommand({
  Bucket: "my-bucket",
  Key: "images/photo.jpg",
  Body: fileBuffer,
  ContentType: "image/jpeg",
}));

• Store images, videos, backups, static websites
• 99.999999999% (11 nines) durability
• Free tier: 5GB storage, 20,000 GET requests/month
• Used by Netflix, Airbnb, Reddit — essentially unlimited scale

EBS — Elastic Block Store

Persistent disk storage attached to EC2 instances. Like a hard drive for your VM.

Database

RDS — Relational Database Service

Managed relational databases. Supports PostgreSQL, MySQL, MariaDB, Oracle, SQL Server.

What RDS handles for you:
✅ Automated backups
✅ Multi-AZ failover
✅ Read replicas
✅ Patching and updates
✅ Monitoring

What you still manage:
- Schema design
- Query optimization
- Instance sizing

DynamoDB — NoSQL Database

Fully managed key-value and document database. Single-digit millisecond performance at any scale.

• No servers to manage
• Auto-scales to handle any traffic
• Free tier: 25GB storage, 25 read/write capacity units

ElastiCache — Managed Redis/Memcached

Managed in-memory caching. Drop-in Redis or Memcached.

Networking

VPC — Virtual Private Cloud

Your own isolated network within AWS. All resources live inside a VPC.

Route 53 — DNS Service

AWS's DNS service. Register domains, route traffic, health checks.

CloudFront — CDN

AWS's global CDN. Cache content at 450+ edge locations worldwide.

Security

IAM — Identity and Access Management

Control who can access what in AWS. The most important security service.

// IAM Policy — allow reading from a specific S3 bucket only
{
  "Version": "2012-10-17",
  "Statement": [{
    "Effect": "Allow",
    "Action": ["s3:GetObject"],
    "Resource": "arn:aws:s3:::my-bucket/*"
  }]
}

Principle of least privilege — give only the permissions needed, nothing more.

Monitoring

CloudWatch — Logs, Metrics, Alerts

Collect logs and metrics from all AWS services. Set alarms.

# View Lambda logs
aws logs tail /aws/lambda/my-function --follow
 
# Create an alarm when CPU > 80%
aws cloudwatch put-metric-alarm \
  --alarm-name "HighCPU" \
  --metric-name CPUUtilization \
  --threshold 80 \
  --comparison-operator GreaterThanThreshold

AWS Global Infrastructure

• Region — geographic area (Mumbai, Virginia, Singapore)
• Availability Zone — isolated data center within a region
• Deploy across multiple AZs for high availability

Typical Web App Architecture on AWS

Users → Route53 (DNS)
      → CloudFront (CDN)
      → ALB (Load Balancer)
      → EC2 / ECS / Lambda (App)
      → RDS (Database)
      → ElastiCache (Cache)
      → S3 (File Storage)
      → CloudWatch (Monitoring)
      → IAM (Security)

Key Takeaway

Start with these 10 — they cover 90% of what you'll need.