OpenAI's newly appointed revenue chief, Denise Dresser , sent a memo to staffers on Sunday, touting the company's alliance with Amazon as a key growth driver for its enterprise business, while noting the constraints of its longstanding tie-up with Microsoft . Dresser's memo lands less than two months after Amazon announced plans to invest up to $50 billion in OpenAI as part of a strategic partnership . Microsoft, Amazon's top cloud computing rival, has invested more than $13 billion in OpenAI