I do not know the answer to your question, but you will find part of it in the makePbKey method in MemcacheSerialization.java . This shows how Java takes an object and makes a key out of it.
, appengine/memcache/memcache.go , AppEngine for Go Item.Key( ). . GetMulti, [] .
, , mkPbKey GetMulti, . , Java String 250, " Go, . ( mkPbKey , 200 , UTF-8. , , .)