When Amazon announces its latest earnings Thursday, we’ll get another glimpse into the battle for market share in cloud computing. It’s grown to nearly a $1 trillion market, thanks to demand from clients ranging from startups to the Pentagon. Amazon has dominated the market, and cloud services generate around half of the company’s profits. But its dominance has been slipping: Microsoft has been snatching cloud clients away from Amazon, and IBM’s success in cloud services helped Big Blue beat analysts’ estimates in its most recent earnings.

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