Updated from July 6 with additional information.

With Amazon.com (AMZN) - Get Report 's second-ever Prime Day on Tuesday, the e-commerce giant is hoping it can outdo its impressive results from last year, when it generated an estimated $400 million in incremental sales and signed up a record number of customers for its all-important Prime Membership program. 

MKM Partners analyst Rob Sanderson wrote in a note last week that Amazon's Prime Day could drive as much as $800 million in sales this year, and have long-lasting benefits for Jeff Bezos' e-commerce empire. 

"We estimate that Prime Day drove an incremental $375-400 million of sales last year. Given that Alibaba's Singles Day grew by 5.6x in its third year and 3.7x in its fourth year (and is now up to $14Bn), we think a double for Prime Day is a realistic assumption," Sanderson noted.

On Tuesday morning, some Amazon customers reported difficulty checking out, but Amazon said in a tweet that it was working to quickly remedy the problem. 

Shares of Amazon, which are up about 11% this year and 62% over the last 12 months were essentially flat at $754.00 in early morning trading on Monday.

Singles Day, which is held every year on Nov. 11 and was created as a sort of anti-Valentine's Day by a group of Chinese college students in the 1990s, has grown to be China's biggest sales day of the year.Alibaba (BABA) - Get Report turned it into a huge commercial event starting in 2009, and last year the company generated $14.3 billion in gross merchandise volume last year, surpassing by far the amount of sales generated in the U.S. on both Cyber Monday and Black Friday. 

Amazon held its first Prime Day last year to commemorate its 20th anniversary, and said at the time it was unsure if it was going to make it an annual event. Last year's sales success, however, ensured that it would be. 

This year,Amazon said it will be offering more than 100,000 deals in 10 countries for Prime Day. The Seattle-based e-commerce giant has also said that it will offer twice as many TVsas it did on Black Friday and Cyber Monday combined. 

Amazon also offered countdown deals for Prime members every day from July 5 to July 11, as well as a sweepstakes for a trip to see musical artists in concert by listening to their playlists on Prime Music. On Tuesday, Amazon is offering a number of deals for its own hardware products, such as a $50 discount on an Amazon Echo and a $30 discount on Amazon Fire TV, as well as many deals on toys, among other categories. 

"AMZN would love to create a summer-time shopping holiday for the mass consumer," Sanderson wrote. "Last year, consumer and media feedback on the event was indicative of a start-up effort with complaints on breadth and inventory. We think expectations are conservative on implied contribution from Prime Day."

Despite the sales generated, Amazon's 2015 Prime Day got a mixed reaction from customers, with many complaining about the product selection and popularizing the hashtag #PrimeDayFail. This year, the increase in the number of deals, third-party sellers that are participating,and added services, such as restaurant delivery, should bode well for its success.

Amazon has invited third-party merchants who use Fulfillment By Amazon (FBA) to submit Prime Day deals this year, and re-invited some of its select sellers from last year. FBA refers to Amazon's network that handles back-end operations, including storage and fulfillment, for third-party sellers.

Amazon revealed earlier this week that the number of sellers participating in Prime Day and the number of deals offered has increased by more than 100% this year. During last year's Prime Day, Amazon revealed that users ordered 34.4 million items, and boasted that it got more new users to try Prime than on any other single day in the company's history.

"What gets me excited about Prime Day -- I think it's an opportunity for the company not only to drive sales outside Black Friday and Cyber Monday, but really push their hardware," said Maxim Group analyst Tom Forte via phone, explaining that specials such as Fire tablet deals have more long-lasting benefits to Amazon.

Bezos' empire has been ramping up Prime Day this year, promoting Prime Now fast delivery services, for example. Amazon could also start to leverage its physical infrastructure and investments in physical stores for Prime Day, Forte said, while acknowledging that such strategies are still in their early stages.

But at the core of Prime Day is Amazon's relentless focus on Prime. The number of Prime members was up 51% worldwide last year, according to Sanderson, and Prime members have always been Amazon's best customers. The membership service has increasingly become one of the most effective ways for Amazon to increase its order volume and frequency among users, said Tigress Financial Partners chief investment officer Ivan Feinseth via phone.

"It's an important part of their overall marketing," he said of Prime, adding that delivery logistics and drone strategies will be among the areas of focus for Amazon Prime going forward. 

A Prime membership costs $99 a year, or $10.99 a month, and offers free two-day shipping for all eligible products. It also includes access to Prime Instant Video, Prime Music, Prime Now and Restaurant Delivery.

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