Amazon's cloud-computing division said revenue jumped 45 percent in the fourth quarter, as the company continued to cement its lead over Microsoft and Google.

Sales at Amazon Web Services climbed to $7.43 billion from $5.11 billion a year ago, topping the $7.29 billion consensus estimate among analysts polled by FactSet. AWS revenue represented 10 percent of total quarterly sales at Amazon.

The cloud business has become crucial to the success of its parent, not only for revenue but also for profits.

Operating income for AWS in the quarter was $2.18 billion, exceeding the $2.09 billion FactSet consensus estimate. The unit accounted for 58 percent of Amazon's overall operating income. AWS' operating margin was 29 percent, shrinking from 31 percent the prior quarter.