The cloudsql_session_read_only session parameter provides a robust, non-circumventable mechanism in Cloud SQL for...

The cloudsql_session_read_only session parameter provides a robust, non-circumventable mechanism in Cloud SQL for PostgreSQL for preventing data modification during a session. You can use this flag to either make a session temporarily read-only, or make a session permanently, irreversibly read-only.

For more information, see Create a read-only session in Cloud SQL for PostgreSQL.