Google App Engine has some information about Memcache limits:
- http://code.google.com/appengine/docs/quotas.html#Memcache
- http://code.google.com/appengine/docs/python/memcache/overview.html#Quotas_and_Limits
However, total allowed size of RAM/memory store for a single application is not specified. It's known that no objects above 1MB is allowed. Do you have information?
The amount of memcache capacity your app has isn't fixed, and may vary depending on the traffic to your app and how it uses memcache.
As of November 2013, App Engine offers dedicated memcache which guarantees a specific amount of memcache RAM. You can purchase between 1 and 20 GB of dedicated cache. More than 20 GB is available upon request.
The shared memcache RAM available to an application still varies based on multiple factors.
来源：https://stackoverflow.com/questions/2175586/how-much-memory-of-memcache-is-available-to-a-google-app-engine-account