Hello Yihang, The App Engine application incurs costs when running. Billing begins when an instance starts and ends fifteen minutes after a manual instance shuts down or fifteen minutes after a basic instance has finished processing its last request. You may find more detail on the "App Engine Pricing" page <https://cloud.google.com/appengine/pricing>. In other words, this mandatory app would not cost you, if your main application runs on a GCE instance.
Datastore usage costs are calculated in terms of stored data, entity reads, entity writes, entity deletes, and small operations. None of these involve the active App Engine application, if the only use you make of the Datastore is from your GCE instance. -- You received this message because you are subscribed to the Google Groups "Google App Engine" group. To unsubscribe from this group and stop receiving emails from it, send an email to google-appengine+unsubscr...@googlegroups.com. To post to this group, send email to google-appengine@googlegroups.com. Visit this group at https://groups.google.com/group/google-appengine. To view this discussion on the web visit https://groups.google.com/d/msgid/google-appengine/7554066e-1424-40c6-b20f-2aa3abbbb3d0%40googlegroups.com. For more options, visit https://groups.google.com/d/optout.
