At some point you'll want to run your own cron jobs. Google App Engine has a really nice support for running cron jobs - read more about it here: Scheduling Jobs with cron.yaml.
In terms of the web app structure, the best option is to have each cron job in a separate Python file inside the "cron" folder. A cron job is just a normal handler that accepts GET requests (it doesn't accept other types of requests, like POST).
One example of a cron job is already created in this starter template. It's a cron job that permanently removes a user object from the Datastore once it has been marked as "deleted".
Since a cron job is a normal handler with its own route (URL is set up in main.py), anyone can call it. But to prevent random people from triggering your cron job handlers, make sure you check each in the beginning of each cron job whether the request has the
X-Appengine-Cron: trueHTTP header (cannot be faked) and whether it comes from the10.0.0.1ip address. Read more about that here.
In addition, you'll need to add each cron job also in the file called cron.yaml in your root where you'll define when
the cron jobs are to be run.