According to The NY Times,
Meltdown is a particular problem for the cloud computing services run by the likes of Amazon, Google and Microsoft. By Wednesday evening, Google and Microsoft said they had updated their systems to deal with the flaw.
Amazon told customers of its Amazon Web Services cloud service that the vulnerability “has existed for more than 20 years in modern processor architectures.” It said that it had already protected nearly all instances of A.W.S. and that customers must update their own software running atop the service as well.