AWS Interface Endpoints provide a secure and reliable way to connect your VPC to supported AWS services and SaaS offerings powered by PrivateLink. By keeping traffic within the AWS network, these endpoints reduce exposure to the public internet and simplify compliance requirements.
This article explains how Interface Endpoints work, when to use them, and how they fit into a broader networking strategy on AWS. You will find practical guidance, configuration details, and real-world scenarios to help you plan and operate secure architectures.
| Endpoint Type | Traffic Path | Use Case | Visibility |
|---|---|---|---|
| Interface Endpoint (ENI) | Private IP within your VPC | Services such as Amazon S3, DynamoDB, Lambda via PrivateLink | Elastic network interfaces, security groups, network ACLs |
| Gateway Endpoint | Through route table to AWS backbone | Amazon S3, DynamoDB | Route tables, VPC endpoints policies |
| Interface DNS hostnames | Private DNS names resolve to private IPs | Service discovery, application whitelisting | Private DNS options, custom DNS resolution |
| Traffic filtering | Security groups and network ACLs | Least-privilege access to services | Policy-based and identity controls |
How AWS Interface Endpoints Work Under the Hood
An Interface Endpoint creates an elastic network interface inside your selected subnets with a private IP address. This interface serves as an entry point for supported AWS services and PrivateLink endpoints, keeping data within the AWS global network.
Security groups and network ACLs attached to the endpoint interface provide fine-grained traffic filtering. Route tables direct traffic destined for the supported service to the endpoint, ensuring that no public internet gateway is required for communication.
Behind the scenes, AWS PrivateLink handles the connectivity between the service producer and consumer, using network isolation and encryption in transit. This model supports many AWS services, including Amazon S3, DynamoDB, and many SaaS offerings available through AWS Marketplace.
Planning High Availability and Redundancy
For production workloads, deploy interface endpoints across multiple Availability Zones to avoid a single point of failure. Each zone gets its own elastic network interface, so AZ-level outages do not interrupt all traffic.
Use VPC endpoints policies to restrict access to specific resources and principals, and combine them with service control policies or IAM identity policies for defense in depth. Consider failover patterns at the application layer, since network interfaces, like other EC2 resources, can be reattached or replaced in the event of failure.
Security and Network Isolation Best Practices
Interface endpoints allow you to keep sensitive workloads off public IP space while still accessing managed AWS services. By using private IP addresses, you reduce exposure to internet-based threats and simplified egress rule management.
Combine Interface Endpoints with VPC endpoints policies, security groups, and AWS PrivateLink endpoint services to enforce least-privilege access. For regulated workloads, this architecture supports compliance objectives by limiting data exposure and providing clear audit trails through VPC Flow Logs and AWS CloudTrail entries.
Monitoring, Cost, and Operational Considerations
Monitor interface endpoints using Amazon CloudWatch metrics for active connections, error rates, and data transfer. VPC Flow Logs provide visibility into traffic patterns at the network interface level, helping you detect misconfigurations or unauthorized access attempts.
Costs include hourly charges per interface and data processing fees, which vary by AZ and payload size. Architect for efficiency by consolidating connections where possible, using DNS hostnames for service discovery, and leveraging gateway endpoints for S3 and DynamoDB to lower overall networking spend.
Operational Recommendations for AWS Interface Endpoints
- Deploy interface endpoints in at least two Availability Zones for high availability.
- Use VPC endpoint policies and IAM conditions to enforce least-privilege access.
- Monitor connection counts and error metrics with Amazon CloudWatch.
- Test failover scenarios to ensure applications handle interface or AZ disruption gracefully.
- Leverage private DNS resolution to simplify service discovery and client configuration.
FAQ
Reader questions
How do interface endpoints affect VPC route table configuration?
You must add a route in your VPC route table pointing the service prefix to the interface endpoint. Without this route, traffic destined for the service will not reach the endpoint and may fall back to a public internet gateway or fail.
Can interface endpoints be used across multiple accounts or VPCs?
Yes, you can create interface endpoints in a shared VPC and access them from other accounts using AWS PrivateLink endpoint permissions and resource policies. Each consumer VPC requires its own endpoint interface in the target subnets.
What happens to traffic if an interface endpoint spans multiple Availability Zones?
Each zone runs an independent elastic network interface, so traffic is isolated per AZ. If one zone becomes unavailable, traffic to that specific endpoint interface fails over only for that AZ, highlighting the need for multi-AZ design in critical applications.
How do security groups and network ACLs work with interface endpoints?
Security groups attached to the endpoint interface control allowed inbound traffic, while network ACLs manage subnet-level rules. Both layers must permit the necessary ports and protocols, typically HTTPS, for service communication to succeed.