As you may know, the default Elastic network interfaces (ENI) is 250 per VPC per region. In most cases, if it exceeds the default limit 250, this could be the cause of the error you are experiencing.

To fix this issue, do one or both of the following:

1. Delete unused elastic network interfaces, you can find more information from https://aws.amazon.com/premiumsupport/knowledge-center/lambda-eni-find-delete/
2. Request a service limit: Sign in to your account and open the AWS Support console. Choose Service Limit Increase. For Limit type, choose Lambda. For Region, choose the AWS region you need the elastic network interfaces in. For Limit, choose Elastic Network Interfaces per VPC. For New limit value, type the number of elastic network interfaces you need.

In addition, I would explain a little bit more here. Hyperplane ENIs are tied to a security group:subnet combination in your account. Functions in the same account that share the same security group:subnet pairing use the same network interfaces. If a combination is shared across multiple functions in your account, we reuse the same network interface across functions.

Some architectural recommendation using HyperPlane ENIs in Lambda function are:

1. Look into reusing these ENI endpoints per function. We only will reuse ENIs if your function has the exact same security requirements (same security groups) as another function within the same subnet.

2. Ensure the old versions of functions are cleaning up such that they aren’t letting unused ENIs be provisioned.

3. Look into splitting across different VPCs to scale your system.