Currently there are:
All of the 10 [appengine] questions currently relates to Google App Engine. I think it would make sense to either retag those or create a synonymic link between those two tags, using [google-app-engine] as the master tag.
Note: I've checked the synonyms page and it appears that this link hasn't been proposed yet.
Note 2: [appengine] tag has no wiki description. [google-app-engine] does.