Here is the situation
I have a model like

```
class Content(ndb.Model):
    likeCount=ndb.IntegerProperty(default=0)
    likeUser  = ndb.KeyProperty(kind=User, repeated=True)

```

When a new content generate than a new "Content" object is generated like

```
content_obj_key = Content(parent=objContentData.key, #Where ContentData is     another ndb.Model subclass
                             likeUser=[],
                             likeCount=0
                           ).put()

```

And when any user like the same content than below function gets called

```
def modify_like(contentData_key, user_key):
    like_obj = Content.query(parent=contetData_key).get()
    if like_obj:
        like_obj.likeUser.append(user_key)
        like_obj.likeCount += 1
        like_obj.put()

```

**Problem:**  

Now the problem is that when at the same time more than 4 user like the same content than this object write wrong data.  

I mean lets say userA, userB, userC and userD like this data at the same time and currently only userE liked the same content.  

So after all new four write the "likeCount" is not 5, always less than 5 and the "likeUser" list length is also less than 5.

So how can I solve this problem?
So that always data remains consistent.