When architecting services on a virtual private cloud, the distinction between a gateway endpoint and an interface endpoint is foundational to security, performance, and cost management. Both mechanisms facilitate private connectivity to specific AWS resources without requiring traffic to traverse the public internet, yet they operate in fundamentally different layers of the network stack. Understanding this difference is critical for engineers who must balance resilience with strict compliance requirements.
Defining the Gateway Endpoint
A gateway endpoint is a specific construct designed exclusively for two AWS managed services: Amazon S3 and DynamoDB. Unlike traditional network appliances, this endpoint leverages the robust infrastructure of the AWS global network to provide a private route directly to these storage and database services. Because it operates at the Virtual Private Cloud (VPC) level, traffic destined for these endpoints never leaves the AWS network, which reduces exposure to internet-based threats and latency spikes.
Technical Mechanics of Gateway Endpoints
Gateway endpoints function by modifying the VPC route table. When you create one, you specify a route table and a target prefix list that corresponds to the supported service. Any traffic within the VPC matching that prefix list is routed privately through the endpoint rather than via an internet gateway, NAT device, or VPC peering connection. This architecture ensures that even if the route table is misconfigured, the traffic cannot egress to the public internet, enforcing a zero-trust model for data at rest.
Defining the Interface Endpoint
An interface endpoint, by contrast, is a more flexible and versatile networking component that provides private connectivity to a vast array of AWS services and even supported AWS Marketplace partner applications. Built on AWS PrivateLink, this endpoint creates an elastic network interface with a private IP address within your subnet. This allows traffic to remain entirely within the AWS private network when communicating with services such as Lambda, SQS, or third-party solutions that support the PrivateLink standard.
Technical Mechanics of Interface Endpoints
Interface endpoints utilize an elastic network interface that listens on a private IP address. To control access, they rely heavily on security groups and network ACLs, allowing for granular permissioning at the instance level. Furthermore, these endpoints can be configured to accept traffic from on-premises data centers via AWS Direct Connect or VPN, provided the VPC and on-premises network are properly peered. This flexibility makes them ideal for microservices architectures where strict segmentation between application tiers is required.
Comparing Security Posture and Network Traffic
While both gateways enhance security by keeping traffic off the public internet, they offer distinct security models. Gateway endpoints implicitly deny all traffic that is not explicitly allowed in the route table, providing a simple but effective chokepoint for S3 and DynamoDB. Interface endpoints, however, rely on the shared responsibility model of security, requiring the user to manage security groups and endpoint policies to control access to the target service.
