I have a dynamic backend process that gets called from within my frontend app code. To do this it must be visible via app.yaml. But when the backend gets run in this way I see no change in my backend quota on the admin panel, leading me to believe it's running on the frontend quota.
The Backend is called via a taskqueue.add(url='/path/to/backend') from the frontend side.
Should this not invoke a backend instance for a minimum of 15 mins and thus use that quota?
You don't target a task to a backend via URL, you do it with the target parameter:
taskqueue.add(url='/my/url', target='my_backend_name')
See the documentation.