Map<Key, Entity> entityMap = datastore.get(keys);
// step 2 : update
List<Entity> updateList = newLinkedList();
for (Key key : infoMap.keySet()) {
EntityUpdateInfo info = infoMap.get(key);
Entity entity = entityMap.get(key);
updateList.add(applyChange(entity, info.getChanges()));
}
datastore.put(updateList);
}