Someone once asked Srila Prabhupada a challenging question.
"Can Krishna make a rock so heavy that He can't pick it up?"
"Yes."
"Then he is not all-powerful."
Prabhupada answered, "Then He will pick it up."
The challenger said, "Then He can't create a rock He can't lift."
Prabhupada said, "Then He will create another rock, then lift it again, and again create and lift. Krishna is always expanding His energy, and then He measures it, then expands it again and measures it. This is the nature of Krishna's pastimes."

From Blazing Sadhus, by Achyutananda Das
p. 209