With new users joining faster than anyone imagined, Facebooks’ servers, packed in a couple of small cages that it rented at a data center in Silicon Valley, were running in overdrive and generating too much heat. So a group of employees at the young startup scattered across the Valley in search of more than two-dozen cooling fans. They found them at local Walgreens (WAG) outlets and managed to install them in the data center just in time to avert a disaster.

Jonathan Heiliger, who joined Facebook a few months later, made sure such near misses wouldn’t happen again. Heiliger, who became Facebook’s vice president of technical operations, led the development of the social network’s infrastructure as it grew from 30 million to more than 800 million users.

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Now Heiliger, who left Facebook late last year, wants to help other successful startups grow without risking meltdown. He is joining North Bridge Venture Partners as a general partner. Besides making investments in promising startups, Heiliger will coach portfolio companies on how to scaletheir infrastructure successfully. “We really needed domain expertise in understanding how these Web businesses scale,” says Paul Santinelli, a general partner at the firm.

Heiliger will also invest in startups that focus on Web infrastructure and help to grow North Bridge’s presence in Silicon Valley. Until now, the Boston-based venture firm, had just three partners in its Valley office. The firm is currently investing its 2008, $500 million fund, and is expected to raise a new fund soon.

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The task of scaling an Internet business is not nearly as glamorous as, say, coming up with a cool service or building a slick consumer product. But it’s an aspect of startup life that entrepreneurs often overlook, sometimes with disastrous results.

Take Friendster. The pioneering social network crumbled under its inability to cope with its own success. As a consequence, Friendster missed a once-in-a-generation opportunity that was later seized by Facebook and is on track to netting tens of billions to investors. It’s a fate that Twitter, with its recurrent “fail whale,” appears to have averted only narrowly.

Before joining Facebook, Heiliger held executive positions at Walmart.com (WMT) and Danger, which made the once popular Sidekick smartphone and was acquired by Microsoft (MSFT). He also served as chief operating officer at Loudcloud, the company co-founded by Marc Andreessen and acquired by HP (HPQ). Heiliger also had an earlier stint as a tech investor, when he founded the corporate venture group for Global Crossing.

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At Facebook, Heiliger led the growth of the company’s infrastructure from a couple of rented cages inside a Santa Clara, California data center, to a global sprawling network that includes two gigantic state-of-the-art facilities that the company built from the ground up in Prineville, Oregon and Forest City, North Carolina. Heiliger also spearheaded the Open Compute Project, which opened up the designs of Facebook’s low-cost, high-efficiency servers and those of its data centers, following an open source model. Since leaving Facebook, he has been advising startups like Square and Box.net.

Heiliger says he will be looking at both consumer applications and infrastructure companies. “I have been working on one investment,” he said. “It’s not ready to come out of the oven yet.”

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