Amazon's cloud business AWS is earning the company big bucks. It has just published its financial reports for the fourth quarter of last year, and it says its revenue is up 45 per cent.

Sales are up from $5.11 billion last year, to $7.43 billion today, even beating analysts estimates which expected $7.29. AWS (Amazon Web Services) now represents 10 per cent of the entire company's quarterly sales.

But besides revenue, profit is also a huge deal, and AWS nailed it there, as well. Operating income was $2.18 billion, also beating analysts' estimates of $2.09bn.

More than half (58 per cent) of Amazon's overall operating income came from AWS. Its operating margin was 29 per cent, down from 31 per cent the quarter before.

"We are getting more and more creative around getting efficiency up and getting our cost of acquisition down," Amazon's chief financial officer, Brian Olsavsky, told analysts on the company's quarterly earnings call on Thursday.

Looking at the company as a whole, holiday quarter sales hit $72.4 billion, up 20 per cent compared to the same period last year. That brings Amazon's total revenue for the year up to $232.9 billion.

However, growth is slowing down. It is now 20 per cent, down to 38 per cent year-on-year.

Amazon's total profit for 2018 is greater than $10 billion.

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