I applied to their career site.

I was contacted within a few days by a recruiter.

They scheduled me for a phone screen within 4 weeks. The phone screen was a video call, collaborating over a Google Docs file.

They asked me to design a multithreaded scheduler.

I implemented an O(1) add and cancel solution and went over MT patterns.

The engineer told me that it was optimal.

When the recruiter called me with my result, he told me the engineer wrote down that my solution was not optimal. Interesting!