Connecting your EC2 instance to Amazon S3 through either a gateway or interface VPC endpoint will result in private and secure communication within the AWS network, avoiding the public internet. However, there are key differences in how they operate and the implications for your S3 access:  

Gateway Endpoint (for S3):

• Functionality: Primarily used for simplifying S3 access within your VPC. It routes traffic to S3 directly through the VPC route tables, without the need for an internet gateway or NAT gateway.  
• Protocol Support: Supports only S3 traffic over the AWS network.
• Performance: Can offer slightly lower latency compared to interface endpoints due to simpler routing.
• Cost: No additional charges beyond standard S3 data transfer fees.
• Limitations: Does not support access to S3 features that utilize public endpoints, such as website hosting or accessing objects through CloudFront distributions.

Interface Endpoint (for S3):

• Functionality: Provides private access to S3 using AWS PrivateLink, allowing you to interact with S3 as if it were a private resource within your VPC.
• Protocol Support: Supports all S3 operations and features, including those that require public endpoints.
• Performance: May have slightly higher latency than gateway endpoints due to the involvement of PrivateLink.
• Cost: Incurs charges for data processed by AWS PrivateLink in addition to standard S3 data transfer fees.
• Advantages: Enables access to all S3 features, including those that rely on public endpoints. Offers enhanced security and granular access control through PrivateLink policies.

Choosing the Right Endpoint:

• Use a gateway endpoint if:
  • You only need to access S3 objects and buckets directly within your VPC.
  • You want the simplest and most cost-effective solution for private S3 access.
• Use an interface endpoint if:
  • You need to access S3 features that utilize public endpoints (website hosting, CloudFront).
  • You require the additional security and access control features of PrivateLink.
  • You are using AWS services that integrate with S3 via PrivateLink.

Ultimately, the choice between gateway and interface endpoints depends on your specific requirements and use cases for S3 within your VPC.