Affirm CEO Max Levchin on the 2.5 second limit that has shaped card payments for 60 years, and how Apple and Google Pay worked around it: "One of the things that's really amazing and subtle about Apple Pay and Google Pay and its interaction with the Visa and Mastercard networks is... Visa and Mastercard have a hard 2.5 second limit on interaction between the network, the issuing bank, and the merchant and the acquiring bank." "And so the whole thing has to happen in 2.5 seconds, or the…