Amazon is a highly sought after company to work for, and today has well over 500,000 employees.

But in the company's early days — when Amazon's headquarters had only just moved from Jeff Bezos' garage into a downtown Seattle office near a heroin-needle exchange and a porn shop — there were far fewer employees. Amazon was only a team of 10 in 1995, and Bezos was still driving packages to the post office himself.

To ensure that the company would retain high standards as it grew, Bezos outlined a simple, three-question test for hiring new employees in his 1998 letter to shareholders, a year after the online bookseller went public.

"It would be impossible to produce results in an environment as dynamic as the Internet without extraordinary people," Bezos wrote of Amazon's workforce, which in three years had ballooned to 2,100 people. "Setting the bar high in our approach to hiring has been, and will continue to be, the single most important element of Amazon.com's success."

Although written 20 years ago, a representative for Amazon confirmed to CNBC Make It that Bezos' thinking is still a part of the company's framework for hiring today.

Here are his three guiding questions for bringing on new talent, according to the 1998 shareholder letter.

1. "Will you admire this person?"

First, Bezos encourages Amazon recruiters to think about their personal opinion of the candidate.

"I've always tried hard to work only with people I admire, and I encourage folks here to be just as demanding," Bezos writes. "If you think about the people you've admired in your life, they are probably people you've been able to learn from or take an example from."

Bezos isn't alone in his thinking. Facebook CEO Mark Zuckerberg also advocates for hiring people whom you respect. "I always tell people that you should only hire people to be on your team if you would work for them," Zuckerberg recently told Recode. Of his own high-ranking employees, like Sheryl Sandberg or Chris Cox, Zuckerberg says, "in an alternate universe, I would be honored to work for any of these people."

2. "Will this person raise the average level of effectiveness of the group they're entering?"

With this question, Bezos is aiming to get a sense of a person's capacity for innovation.

"We want to fight entropy," Bezos writes in the 1998 shareholder letter. "The bar has to continuously go up. I ask people to visualize the company 5 years from now. At that point, each of us should look around and say, 'The standards are so high now — boy, I'm glad I got in when I did!'"

Amazon is known as a demanding work environment, and high standards remain at the core of the company that has made Bezos the richest man in the world.

"Leaders have relentlessly high standards," according to Amazon's statement of its 14 driving principles. "Many people may think these standards are unreasonably high. Leaders are continually raising the bar and drive their teams to deliver high quality products, services and processes."

To ensure that it is hiring the best and brightest, Amazon even appoints a group of its current employees as "bar raisers." On top of their day jobs in various sectors of the company, these employees are tasked with providing additional perspective on new hires around culture fit and talent.

3. "Along what dimension might this person be a superstar?"

It's equally important to consider a candidate's individual talents, according to Bezos.

"Many people have unique skills, interests, and perspectives that enrich the work environment for all of us. It's often something that's not even related to their jobs," he writes in the 1998 letter, citing at the time his excitement about having hired a National Spelling Bee champion.

"I suspect it doesn't help her in her everyday work, but it does make working here more fun if you can occasionally snag her in the hall with a quick challenge: 'onomatopoeia!,'" he writes.

Bringing a unique perspective to work is another of Amazon's 14 principles. "Leaders create and communicate a bold direction that inspires results," according to the company. "They think differently and look around corners for ways to serve customers."

For young people hoping to score a job at Amazon, the company's Worldwide Operations Talent Acquisition Director Sean Kelley tells CNBC Make It that familiarity with those 14 principles is key for getting hired.

"The leadership principles are the playbook," says Kelley. "It's super straightforward… All you really have to do is tell us stories that align with those principles and help us help you."

As for Bezos' questions, even beyond Amazon, the list could be a helpful tool to use before any interview. Adora Cheung, a partner at prestigious Silicon Valley accelerator Y Combinator, says she reflects on the letter before hiring anyone.

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"It's a great, simple rubric," she says.