AWS Public vs Private Services

Public Services

• Definition: Services that can be accessed directly over the internet (public endpoints).

• Why: To allow customers, apps, or users worldwide to use AWS services without being inside a private network.

• How: They expose publicly routable IP addresses (AWS-managed endpoints), and you secure access using IAM, security groups, and firewalls.

✅ Example:

• S3 bucket endpoint (https://bucket-name.s3.amazonaws.com) is accessible over the internet (unless you restrict it).

• AWS Lambda API endpoint can be public if exposed through API Gateway.

Private Services

• Definition: Services that run inside your VPC (Virtual Private Cloud) and do not have public internet endpoints by default.

• Why: To keep sensitive workloads, databases, and applications private and secure inside your isolated AWS network.

• How: You connect using private IPs, VPC endpoints, Transit Gateway, Direct Connect, VPN, etc. No exposure to the public internet.

✅ Example:

• An RDS database in a private subnet — you can’t connect unless you’re inside the VPC or use a VPN.

• Elastic Network Interfaces (ENIs) are private resources.

Why does AWS separate them?

1. Security: Keep sensitive data off the internet.

2. Scalability: Public services provide global access; private services provide isolated control.

3. Flexibility: You decide what stays public (website, CDN) vs. private (databases, backend apps).

4. Compliance: Some workloads (like banking/healthcare) must stay in private networks.

How does AWS make this work?

• Public services → AWS manages internet-facing endpoints, secured by IAM, WAF, Security Groups.

• Private services → Run in your VPC with no internet exposure. You access them through VPC endpoints, private IPs, or VPNs.

List of AWS Public vs Private Services

Public-facing AWS services (Internet-accessible endpoints):

• Storage & Content Delivery

  • Amazon S3

  • Amazon CloudFront (CDN)

  • Amazon Route 53 (DNS service)

• Compute

  • AWS Lambda (when triggered via API Gateway)

  • Amazon API Gateway

  • AWS Amplify (web/mobile hosting)

  • AWS Elastic Beanstalk (can be public apps)

• Networking

  • AWS Global Accelerator

  • AWS Direct Connect (public side of connection)

  • AWS VPN endpoints (customer side connects over public internet)

• Other

  • Amazon SES (email sending)

  • AWS SNS (if using public endpoints)

  • AWS Cognito (user authentication APIs)

Private AWS services (Inside VPC only, no public internet):

• Databases

  • Amazon RDS (in private subnet)

  • Amazon Aurora

  • Amazon DynamoDB (via VPC Endpoint for private use)

  • Amazon Redshift

• Compute

  • Amazon EC2 instances (private subnet)

  • ECS tasks & EKS pods in private subnets

• Networking

  • Elastic Network Interfaces (ENIs)

  • VPC Peering

  • Transit Gateway

• Storage & Data

  • EBS volumes

  • FSx for Windows/Linux

  • Elastic File System (EFS)

• Security & Identity

  • AWS KMS (via private VPC endpoint)

  • AWS Secrets Manager (private via VPC endpoint)

Hybrid (Can Be Both Public or Private Depending on Setup)

• RDS (can be public or private)

• EC2 (can have public IP or private-only)

• Lambda (can run in private VPC or public)

• API Gateway (can expose public API or private API)

• S3 (can allow public access or restrict to VPC endpoint only)

In simple words:

• Public = internet-facing (global access, scalable).

• Private = VPC-only (secure, isolated, sensitive workloads).