CODE EXAMPLE FOR PYTHON

django annotate

from datetime import timedelta
from django.utils import timezone
from django.db.models import Count, Q # need import

Article.objects.annotate(
    numviews=Count(
        'readership__reader__id', 
        filter=Q(readership__what_time__gt=timezone.now() - timedelta(minutes=30)), 
        distinct=True
    )
)


from django.db.models import Count, Case, When, IntegerField
Article.objects.annotate(
    numviews=Count(Case(
        When(readership__what_time__lt=treshold, then=1),
        output_field=IntegerField(),
    ))
)