In fulfilling online orders, Amazon.com Inc. is all about expediency. The fewer people involved the better.

But when it comes to filling higher-level jobs, the e-commerce giant is in no rush—and it has a gantlet of people, dubbed "bar raisers," who must sign off on would-be hires.

Bar raisers are skilled evaluators who, while holding full-time jobs at the company in a range of departments, play a crucial role in Amazon's hiring process, interviewing job candidates in other parts of the company. With a word, they can veto any candidate, even if their expertise is in an area that has nothing to do with the prospective employee's.

Amazon believes the program, created in the company's infancy and honed by founder and Chief Executive Jeff Bezos, screens out cultural misfits and helps make the e-commerce giant a feared competitor in fields as diverse as logistics, tablet manufacturing and television production.

"There is no company that sticks to its process like Amazon does," says Valerie Frederickson, whose eponymous Menlo Park, Calif., human-resources consultancy works with Silicon Valley companies including Facebook Inc. and Twitter Inc. "They don't just hire the best of what they see; they're willing to keep looking and looking for the right talent."