The error message suggests that you may need to look into the specific permissions and roles.

To set the cross-project permissions in a moderately complex architecture in Google Cloud Platform. You will need to configure the roles and permissions.

As per this official document about BigQuery IAM roles and permissions:

This document provides information on Identity and Access Management (IAM) roles and permissions for BigQuery. IAM lets you grant granular access to specific BigQuery resources and helps prevent access to other resources.

The error you are getting due to the cloud Functions can’t read from bigquery because it doesn’t have permissions. So, you need to allow the cloud Functions to read the bigquery in project-2

In your project-1 you need to grant the kubernetes pod permission to call the cloud function.

In your project-2 You need to grant the IAM service Account the roles/bigquery.dataviewer and roles/bigquery.dataEditor

The above roles grant the IAM service account necessary permissions to bigquery tables in Project-2