Answer by Ciprian Tarta for select_related or select_prefetched after calling filter()?

Yes you canAs you can see:

type(MyModel.objects.filter(pk=1))<class 'django.db.models.query.QuerySet'>type(MyModel.objects.filter(pk=1).select_related())<class 'django.db.models.query.QuerySet'>type(MyModel.objects.filter(pk=1).select_related().filter(name='test'))<class 'django.db.models.query.QuerySet'>

All of them are QuerySets