There were multiple interviews: recruiter screen, hiring manager screen, onsite interview (3 rounds - hiring manager, VP of engineering, peer product manager interview), and then take home case assignment. There might be another round but I didn't make it that far

Received a verbal offer from Ambient, but it was rescinded because I couldn’t get in touch with my most recent or skip manager at Amazon for a reference. I provided 6 references (5 from Amazon), all at equal or higher levels, who could speak to my work and character. One was a former manager I reported to at Amazon, just not the most recent one. Several people I reached out to mentioned they weren’t supposed to do reference calls due to Amazon policy (they require using TheWorkNumber), which I confirmed with Amazon HR. The ones who agreed were doing me a huge favor. I was upfront about all of this with Ambient and provided phone numbers for HR and instructions for the background check. Posting this so future candidates know what to expect and can plan ahead in case they face the same kind of situation.