The website processes around 750 deliveries a day and growing at around 25 percent per month, according to the company.
Apple's online sales jumped 24 percent last year.
The company's strong growth indicates that more people are checking the site for digital coupons before making an online purchase.
Wal-mart's e-commerce operation represents its fastest-growing business and helped the company increase total sales last year in what was an otherwise weak year.
The software will helps make international online purchasing and shipping simple for consumers.
Amazon shoppers can now buy items from within Twitter.
The store is a subsection of the site's e-commerce portal.
The additional funding has raised the value of the company to around $15 million.