Alphabet Inc. said its cloud computing unit had a $514 billion backlog of contracted work that hasn’t been recorded as revenue yet, signaling robust demand for its services that underpin the artificial intelligence boom.The backlog for the second quarter, disclosed during the Google parent company’s earnings report Wednesday, was up from roughly $460 billion in similar contracts held during the prior period. Alphabet has been hustling to meet customer demand for its AI services, including sellin...