Amazon Just Had Its Biggest Sales Day Ever

So much for concerns that the second Prime Day event didn't live up to Amazon's expectations.

The online retailer said Wednesday that the self-created holiday was its biggest sales day ever, with worldwide orders rising more than 60 percent compared with the previous Prime Day. In the U.S., orders rose by more than 50 percent.

The company declined to share how many people signed up for Prime to participate in the sale. To qualify for the sales event, which was created last year to celebrate Amazon's 20th birthday, shoppers need to be members of the service.

Amazon shares were roughly flat, near $747, in late morning trading Wednesday.