(Reuters) - Three of the Wall Street's heavyweight technology firms have reported better-than-expected sales at their cloud computing units in recent days, as interest in artificial intelligence drives a rebound in spending by corporate customers.

Growth in the $270 billion cloud infrastructure market, a cash engine for Amazon.com, Microsoft and Alphabet, gives the clearest sign yet that AI investment is bearing fruit after investors drove those stocks to record highs, thanks to optimism about the emerging technology.