The Modules API provides functions that return information about the current operating environment (module, version, and instance). The Modules API also has functions that retrieve the address of a module, a version, or an instance. This allows an application to send requests from one instance to another, in both the development and production environments. You must import the `google.appengine.api.modules` module from the SDK. from google.appengine.api import modules The following code sample shows how to get the module name and instance id for a request: module = modules.get_current_module_name() instance_id = modules.get_current_instance_id() self.response.write( 'module_id={}&instance_id={}'.format(module, instance_id)) The instance ID of an automatic scaled module will be returned as a unique base64 encoded value, e.g. `e4b565394caa`. You can communicate between modules in the same app by fetching the hostname of the target module: backend_hostname = modules.get_hostname(module='my-backend') url = "http://{}/".format(backend_hostname) try: result = urllib2.urlopen(url).read() self.response.write('Got response {}'.format(result)) except urllib2.URLError: pass You can also use the [URL Fetch](https://docs.cloud.google.com/appengine/docs/standard/services/urlfetch/outbound-requests) service.