One of Walmart Inc’s best chances at taking on Amazon.com Inc in e-commerce lies with six giant server farms, each larger than 10 football fields.

These facilities, which cost Walmart millions of dollars and took nearly five years to build, are starting to pay off. The retailer’s online sales have been on a tear for the last three consecutive quarters, far outpacing wider industry growth levels.

Powering that rise are thousands of proprietary servers that enable the company to crunch almost limitless swathes of customer data in-house.

Most retailers rent the computing capacity they need to store and manage such information. But Walmart’s decision to build its own internal cloud network shows its determination to grab a bigger slice of online shopping, in part by imitating Amazon’s use of cloud-powered big data to drive digital sales.

The effort is helping Walmart to stay competitive with Amazon on pricing and to tightly control key functions such as inventory. And it is allowing the company to target shoppers with more customised offers and improved services, two top executives said in interviews at Walmart’s San Bruno and Sunnyvale campuses in California.

“It has made a big difference to how fast we can grow our e-commerce business,” said Tim Kimmet, head of cloud operations for Walmart.

He said Walmart, for example, is using cloud data to stock items frequently ordered by customers via voice shopping devices such as Google Home.

The network is helping the retailer improve its in-store operations as well. Using data gleaned from millions of transactions, the company sped up the process by which customers can return online purchases to their local stores by 60 per cent. And Walmart can adjust prices at its physical locations almost instantly across entire regions.

“We are now able to execute change faster,” Jeremy King, Walmart’s chief technology officer, said.