Affirm shares soared 30% in premarket trading.The company made an announcement, according to which it has expanded its relationship with Amazon to serve as Amazon's only third-party, non-credit card, buy now, pay later option in the U.S. Affirm will generally be available for all eligible purchases of >$50 on Amazon.com and the Amazon shopping app in the U.S, with consumers having the option to split the total cost of eligible purchases into monthly payments at checkout.