Amazon (NASDAQ: AMZN) investors likely know the company's most visible business -- e-commerce operations -- isn't its most profitable. Instead, the company's smaller cloud business, Amazon Web Services (AWS), is its most profitable on account of higher margins. Last fiscal year, AWS produced 105% of Amazon's operating income as losses in international retailing offset North American retailing profit.Therefore, it's key for investors to pay close attention to Amazon's market position in cloud computing.