It's been nearly a year since Amazon bought smart doorbell company Ring for a whopping $1 billion.

Ring — which was once on the brink of going broke and got rejected by investors on ABC's "Shark Tank" — is the ultimate Cinderella story.

Founder Jamie Siminoff landed a coveted spot on "Shark Tank" (yes, the show where he was rejected) as a guest judge for season 10. As for working with Amazon, Siminoff told CNBC Make It in October that the experience has been incredibly positive.

"It's a great place for an inventor to go who wants to continue to invent and impact the world," Siminoff said. "That's really all I wanted to do. At the end of the day, I called myself a 'chief inventor' at Ring, I didn't call myself a CEO for a very specific reason, which is that I like inventing and building product much more than building a business.

"Now at Amazon, I have the ability to focus on that and not focus as much on the things of the business, like the funding of it."

Siminoff has met personally with the world's richest man, Amazon founder and CEO Jeff Bezos, and while he admits his interaction with Bezos has been limited, he says he's learned a lot and been impressed by the famous entrepreneur.

"I think the most impressive thing...[is that he's] a very real person who also you can tell has this like insatiable appetite for invention and learning and seeing what's out there and doing that, and like very curious," Siminoff told CNBC Make It. "So all of my interactions with him so far have been very fun...we've been sort of talking about these things that we can do...brainstorming with him on it, and he's been very valuable at that. So it's been really kind of cool."

Amazon did not respond to CNBC Make It's request for comment.

But before he was rubbing elbows with Bezos, Siminoff struggled. In fact, there was a time when he thought his company might go broke.

Siminoff went on "Shark Tank" in 2013, pitching a business that was then called Doorbot. It sold a WiFi-enabled doorbell that allowed users to see video of and talk to people as they arrived at the front door. All of the investors but Kevin O'Leary passed, and he made what Siminoff considered an unacceptable offer. Doorbot didn't make a deal.

"I remember after that 'Shark Tank' episode literally being in tears," Siminoff told CNBC Make It in a previous interview. "I needed the money, we were out of money at the time."

He'd sunk $10,000 into building props for the pitch, and the company's staff of eight had spent a month preparing for the show, according to his blog. After leaving without an investor, it seemed the effort may have been a waste they couldn't afford.

But Siminoff wasn't just upset about the money. The critiques from investors like Mark Cuban and Lori Greiner about the product's ability to sell were fresh objections mirroring others' doubts about his idea. "I can't count the number of people who didn't invest in this, who said 'no,' the number of people who said it was going to fail," Siminoff said. "I don't think [Microsoft] Excel could hold the number of records for it."