🚪 “Why Go Public When You Can Stay Private?” — A Simple Guide to AWS VPC Endpoints

While working in the cloud, your resources often need to communicate with other AWS services, such as S3 or DynamoDB. However, does this communication always have to go through the internet?

The answer is no.

Welcome to the world of VPC Endpoints — a powerful solution for keeping your traffic private, secure, and cost-effective.

🌐 What is a VPC?

Before we explore endpoints, let's cover the basics.

• A VPC (Virtual Private Cloud) is your private data center within AWS.
• It enables you to launch resources, such as EC2 instances or databases, in a virtual network.

🚧 The Challenges of Public Access

By default, when your resources need to connect to AWS services like S3, they do so through the public internet. There are two ways to do this:

• Using an Internet Gateway (IGW)
• Using a NAT Gateway (if the resources are in private subnets)

This approach introduces additional costs, increased complexity, and potential security risks.

✅ The Solution — VPC Endpoints

VPC Endpoints enable private connections to AWS services without using the internet.

Benefits:

• ✅ Enhanced Security: There is no exposure to the public internet.
• ✅ Cost-Effective: You can avoid charges associated with NAT Gateways.
• ✅ High Availability: Built-in redundancy ensures reliability.
• ✅ No Bandwidth Bottlenecks: Enjoy optimal performance without limitations.

🛣️ Two Types of VPC Endpoints

1️⃣ Gateway Endpoint (For S3 and DynamoDB)

• Cost: Free to use
• Functionality: Updates the route table in your VPC
• Traffic Management: Ensures that traffic to S3 and DynamoDB remains within AWS's private network
• Note: A prefix list (such as pl-xxxxxxx) is created and used in security groups and routing tables

2️⃣ Interface Endpoint (For all other AWS services)

• Interface Endpoint creates an Elastic Network Interface (ENI) in the subnet with a private IP address.
• Allows you to communicate with AWS services such as SNS, SQS, and Secrets Manager with the help of ENI.
• There is a small hourly cost associated with the Interface Endpoint, along with data transfer charges.

Additionally, it supports PrivateLink, enabling VPC-to-VPC communication without concerns about IP address conflicts.

🔄 Common Use Cases

• Accessing S3 buckets from Lambda functions or EC2 instances within a private subnet.
• Connecting privately to SaaS providers or other VPCs using AWS PrivateLink.
• Ensuring all data transfers remain internal to comply with security policies.

📌 Security Tip

If your security group does not allow outbound traffic by default, add a prefix list (for S3 or DynamoDB) or the private IP of the Interface Endpoint to the outbound rules.

💡 Think of it this way:

• Gateway Endpoint: This is like a dedicated shortcut to the AWS service.
• Interface Endpoint: This is similar to a private door within your house that leads directly to the service provider, allowing you to access it without going outside.

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