Background

I have an .NET Core Web API hosted on the AWS Lambda. I put the AWS Gateway in front.

Problem

I am getting the “500 Internal Server Error” when accessing the Web API’s swagger url. We already checked the API/Lambda invoke permission. If you are not sure, you can check this link

Solution

The solution is that you need to redeploy your API gateway.

If you are using Terraform to deploy the AWS AG, you need to this code.

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/* 
    Forcing the API deployment even there is no change. 
    We will might have to explore this option ``redeployment = sha1(jsonencode([ in future```
    https://registry.terraform.io/providers/hashicorp/aws/latest/docs/resources/api_gateway_deployment#terraform-resources
  */

  variables = {
     deployed_at = "${timestamp()}" 
  }

If it’s the permission, you can confirm by looking at this message “Invalid permissions on Lambda function” in the CloudWatch log.