Architect Data Action Lambda Invocation 403: IAM Role Configuration Issue

Looking for advice on resolving a persistent 403 Forbidden error when invoking an AWS Lambda function from a Genesys Cloud Architect Data Action.

I have configured the Data Action with the correct Lambda ARN and endpoint. The integration test within the Architect UI succeeds, confirming the IAM role attached to the Genesys Cloud integration has the lambda:InvokeFunction permission. However, when executed in a live flow, the response payload contains a generic error object:

{
 "code": 403,
 "message": "User: arn:aws:iam::123456789012:role/gc-integration-role is not authorized to perform: lambda:InvokeFunction on resource: arn:aws:lambda:eu-west-1:123456789012:function:my-flow-function"
}

My IAM policy is explicitly defined as follows:

{
 "Version": "2012-10-17",
 "Statement": [
 {
 "Effect": "Allow",
 "Action": "lambda:InvokeFunction",
 "Resource": "arn:aws:lambda:eu-west-1:123456789012:function:my-flow-function"
 }
 ]
}

I have verified that the region in the ARN matches the Lambda function’s region (eu-west-1). The Genesys Cloud integration uses a role that is assumed via a trust policy. Could this be a cross-account trust issue where the Genesys Cloud principal is not explicitly allowed in the Lambda function’s resource-based policy, or is there a subtle mismatch in how the Data Action constructs the authorization header?

You might want to check at the resource policy on the Lambda side, not just the IAM role. Add this statement to the function’s policy: {"Effect":"Allow","Principal":"*","Action":"lambda:InvokeFunction","Resource":"arn:aws:lambda:us-east-1:ACCOUNT_ID:function:FUNCTION_NAME","Condition":{"StringEquals":{"aws:SourceArn":"arn:aws:execute-api:us-east-1:ACCOUNT_ID:API_ID/*/*/*"}}}.

If I remember correctly, relying on Principal: * with a source ARN condition is a known anti-pattern that breaks when Genesys rotates its API Gateway IDs, causing intermittent 403s in production.

Use the IAM role ARN directly in the resource policy instead of wildcarding with conditions.

Check your Lambda resource policy to ensure it explicitly allows the Genesys Cloud account root as the principal, rather than using a wildcard. The point above is correct that Principal: * is fragile because Genesys rotates API Gateway IDs behind the scenes, which invalidates the aws:SourceArn condition you might be relying on. In my ServiceNow integration pipelines, I switched to a static account-level trust relationship to avoid these intermittent 403s during rotations. You need to update the policy to target the specific Genesys AWS account ID associated with your organization.

Here is the exact JSON statement you should append to your Lambda’s resource policy. Replace GENESYS_ACCOUNT_ID with the ID provided in your Genesys Cloud integration settings. This ensures that even if the underlying API Gateway ARNs change, the invocation remains authorized as long as the request originates from the correct Genesys account.

{
 "Effect": "Allow",
 "Principal": {
 "AWS": "arn:aws:iam::GENESYS_ACCOUNT_ID:root"
 },
 "Action": "lambda:InvokeFunction",
 "Resource": "arn:aws:lambda:us-east-1:YOUR_ACCOUNT_ID:function:YOUR_FUNCTION_NAME"
}

This approach decouples your Lambda security from Genesys’ internal infrastructure changes. I usually verify this by checking the CloudWatch logs for the Lambda execution; if the policy is correct, you should see a successful START record without any IAM denial errors.

You need to pin the principal to the Genesys Cloud account root instead of using a wildcard. Rotating API Gateway IDs invalidate aws:SourceArn conditions, so explicit trust is required.

"Principal": { "AWS": "arn:aws:iam::GENESYS_ACCOUNT_ID:root" }