The e-commerce innovation arm of Wal-Mart Stores Inc. has bought web site acceleration firm Torbit. It is the fourth technology acquisition for Wal-Mart in recent months.

Established in 2010, Torbit offers two primary services. Torbit Insight provides web site performance data, and Torbit Site Optimizer helps web sites render content to consumers faster, such as by compressing files and sending content that works best for the web browser being used. @WalmartLabs, in a blog post announcing the acquisition, says it plans to use Torbit’s technology to “help us create a faster, more customized and flexible experience for our online customers.” That includes optimizing sites for customers shopping Walmart.com from desktop computers, tablets and mobile phones, Wal-Mart says.

Wal-Mart did not say what or how it paid for Torbit. Torbit has notified its existing clients, which include several e-retailers ranked in Internet Retailer’s Top 500 Guide, that they have 30 days to transition off Torbit’s services, a Wal-Mart spokeswoman says. According to a client list on Torbit’s web site, e-retailer clients include Build.com (No. 80), Wayfair LLC (No. 52) and CafePress.com (No. 110). Torbit investors include K9 Ventures and Trinity Ventures. Trinity’s other e-commerce investments include mobile commerce site and app builder Moovweb and e-retailers BeachMint and Blue Nile.

@WalMartLabs in May said that it planned to add more than 150 employees to its e-commerce technology team in Silicon Valley by July. The Torbit acquisition adds four engineers to the retailer’s e-commerce staff. 

Wal-Mart’s purchase of Torbit follows its June acquisition of predictive analytics firm Inkiru Inc., and the acquisitions of e-commerce development company OneOps and social media software development firm Tasty Labs, both in May. Those three acquisitions added at least 10 employees to Wal-Mart’s e-commerce division.