count_sample.py

# slower because it loads all products into Python memory to execute 'len()'
%timeit len(Product.objects.all())                                                                                                                                                                                                                   
3.47 ms ± 36 µs per loop (mean ± std. dev. of 7 runs, 100 loops each)


# faster because an SQL expression executes this
%timeit Product.objects.count()                                                                                                                                                                                                                      
267 µs ± 7.51 µs per loop (mean ± std. dev. of 7 runs, 1000 loops each)