App Runner Data Transfer Out and Nat Gateway Data Processing Bytes Cost.

Question

Hi all,

We have some App Runner services running, and outbound traffic is configured to use a VPC Connector to access our VPC resources. I wanted to clarify how AWS charges for data transfer in this setup:

When the App Runner service makes requests to external services on the Internet, does the data transfer out cost include both the outbound request and the inbound response, since the traffic passes through the VPC?

In this configuration, when the service accesses the Internet, is the traffic routed through a NAT Gateway via the VPC Connector, or does App Runner handle Internet-bound traffic differently?

I’m trying to understand why our App Runner data transfer costs appear higher than expected and want to confirm the billing behavior in this setup.

Thanks in advance for any clarification!

SHAJAM · Accepted Answer

How much data are you expecting to transfer and how much is it actually transferring? Well, if you are transfer data, you will be charged for data transfer after your free usage period. Even if you use private link / private endpoints, there will be a different processing fee.

By any chance, if you are transferring data to S3 or DynamoDB, you can setup VPC gateway endpoint and update your route table to use those endpoints - that will reduce the those costs.

re:Post Agent · Answer

When your App Runner service uses a VPC Connector to access resources, there are a few important aspects to understand about data transfer costs:

For data transfer charges, AWS typically charges for outbound traffic (data leaving AWS to the internet), while inbound traffic (data coming into AWS from the internet) is generally free. This means that when your App Runner service makes requests to external services on the internet, you're primarily charged for the response data coming back from those external services to your App Runner service, not the outbound request itself (unless the request contains significant data).

When you use a VPC Connector with App Runner, internet-bound traffic is indeed routed through a NAT Gateway in your VPC. This routing path incurs two types of charges:

1. NAT Gateway data processing charges: You pay for each gigabyte of data processed by the NAT Gateway, regardless of direction (both incoming and outgoing).

2. Data transfer out charges: You pay for data transferred from AWS to the internet.

The higher-than-expected costs you're seeing could be due to the combination of these charges. Since your traffic is going through the NAT Gateway, you're paying both for the NAT Gateway data processing (in both directions) and for the data transfer out to the internet.

To optimize costs, you could consider:
- Creating gateway VPC endpoints for AWS services that support them (like S3 or DynamoDB) to bypass the NAT Gateway
- Ensuring your NAT Gateway is in the same Availability Zone as your resources to minimize cross-AZ data transfer charges
- Analyzing your application's traffic patterns to identify opportunities for reducing data transfer  
**Sources**  
[Data Transfer Charges | AWS re:Post](https://repost.aws/questions/QU4VRRUOm_QnSh5rO5DctX8g/data-transfer-charges)  
[AWS Network Firewall Pricing – Network Security Service – Amazon Web Services](https://aws.amazon.com/network-firewall/pricing/)  
[Pricing for NAT gateways - Amazon Virtual Private Cloud](https://docs.aws.amazon.com/vpc/latest/userguide/nat-gateway-pricing.html)

App Runner Data Transfer Out and Nat Gateway Data Processing Bytes Cost.

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