I applied online. A recruiter sent me an email and set up a phone interview with a Senior Software Engineer at Google. I don't know whether to call this my worst experience or the best.

The recruiter sent me a few documents which were already available on the internet. As expected, the interviewer asked something I had never heard or seen before. It was not a difficult question, but it was very vague and open-ended, requiring a lot of assumptions.

From the very second we started our phone interview, the interviewer said hi and immediately began with the question. As we proceeded, the interviewer kept saying yes to every assumption and design choice I made, never interrupting me. Once I was done writing the code, he pointed to a couple of variables in my code and asked me for the reason for using them. I explained, and it was 45 minutes already. So, he disconnected the phone call, bidding me goodbye and saying the recruiter would be in touch regarding the feedback.

The recruiter was a sweet person. She called me 4 days later to let me know they wouldn't be proceeding further. She added that she couldn't share what kind of feedback led to this decision because of Google's recruitment policy. She told me to reach out to her after a year if I was still interested and also mentioned that people who work at Google usually interview with them at least twice before getting hired.

This is a very open-ended system design question, and you need to write a program for it.