Like Azure last week, AWS reported some slippage in its cloud earnings growth numbers today, dropping from 49 percent growth last year at this time to 37 percent this year. Total revenue increased from Q2 last year from $6.105 billion to $8.381 billion this year. Today’s report puts the company on an astonishing run rate of over $33 billion — just for AWS. That’s a successful company, nevermind one that’s a division of a larger organization.

And Amazon has to be thrilled that it is, as AWS accounted for 13 percent of the company’s total income this quarter, as it continues to help lead the way for the online retailer. All of that is mostly good news by most measures, but the slowing growth in a market that is continuing to accelerate is curious for both Microsoft and Amazon, as both companies continue to dominate the cloud infrastructure market.

Amazon controls approximately 33 percent of the market, while Microsoft accounts for around 16 percent. Regardless of whose numbers you look at, AWS has approximately double the marketshare of Microsoft, but Microsoft remains the only company with double digit marketshare up until this point.

The drop by both companies could simply be attributed to the law of large numbers, which says as big as these two companies are, sustaining the kind of growth rates they were on becomes increasingly difficult over time, even in an accelerating market.

“What we are seeing is the law of large numbers where the revenue gets so high, the growth percent gain gets harder. AWS’s dollar gain is still larger than the number 2-5 [rivals] combined,” Patrick Moorhead, principal analyst at Moor Insights & Strategy told TechCrunch.

As markets mature, growth just naturally slows down, and Amazon couldn’t maintain growth in the 40s forever no matter how hot the market is. Regardless, the revenue remains impressive and AWS continues to help drive Amazon’s success.