Idiots guide to app engine and memcache
About reference properties, let's say you have MainModel and RefModel with a reference property 'ref' that points to a MainModel instance. Whenever you cal ref_model.ref it does a datastore get operation and retrieves the object from datastore. It does not interact with memcache in any way.
I am struggling to find a good tutorial or best practices document for the use of memcache in app engine.  
I'm pretty happy with it on the level presented in the docs.  Get an object by ID, checking memcache first, but I'm unclear on things like:
If you cache a query, is there an accepted method for ensuring that the cache is cleared/updated when an object stored in that query is updated.
What are the effects of using ReferenceProperties ? If a cache a Foo object with a Bar reference.  Is my foo.bar in memcache too and in need of clearing down if it gets updated from some other part of my application.
I don't expect answers to this here (unless you are feeling particularly generous!), but pointers to things I could read would be very gratefully received.