Django social network application - database schema

Question

I am writing a simple social media application in Django. I would like to know whether the following model structure is correct, or how can I improve the schema to get better performance. Do I need to split the following relation into a separate model? Like in this question

Models.py

class User(AbstractBaseUser, PermissionsMixin):
 """
 Custom user model with email as username
 """
 email = models.EmailField(unique=True)
 first_name = models.CharField(max_length=75, blank=True, null=True)
 last_name = models.CharField(max_length=75, blank=True, null=True)
 date_joined = models.DateTimeField(auto_now_add=True)
 date_of_birth = models.DateField(validators=[validate_dob],
 blank=True, null=True)
 is_active = models.BooleanField(default=True)
 is_staff = models.BooleanField(default=False)
 avatar = models.URLField(blank=True, null=True)
 followers = models.ManyToManyField("self", blank=True,
 symmetrical=False,
 related_name='following')
 objects = UserManager()
 USERNAME_FIELD = 'email'
 REQUIRED_FIELDS = []
 def __str__(self):
 return self.email
 @property
 def age(self):
 current_year = datetime.datetime.today.year
 return current_year - self.date_of_birth.year
 def get_full_name(self):
 return '{} {}'.format(self.first_name, self.last_name)
 def get_short_name(self):
 return self.first_name
class Post(models.Model):
 title = models.CharField(max_length=45)
 description = models.CharField(max_length=144)
 author = models.ForeignKey(User, on_delete=models.CASCADE)
 published_on = models.DateTimeField(auto_now_add=True)
 class Meta:
 ordering = ['published_on']
 def __str__(self):
 return self.title

To prepare the feed for a requested user, I would like to use the query,

u1 = User.objects.first()
posts = Post.objects.filter(author__in=u1.following.all())