According to HR, there are supposed to be three rounds:

1. Data Structure and Algo & hiring manager
2. Systems Design (High level)
3. Culture and fitment (I believe; I don't recollect very well)

The first round was a very pleasant experience with the hiring manager. They asked a simple question based on arrays.

Second round was postponed several times as the Principal wasn't available. Not sure why they schedule when the Principal's availability is uncertain.

On the day of the interview, the Principal joined in 15 minutes late, only after calling HR for 10 minutes (even HR wouldn't pick up the phone).

Finally, onto the question, it was a simple app, but the constraint given was it should be cost-effective. Expecting 1 million requests per day.

I was able to provide two solutions: aggressively cost-effective, and moderately cost-effective with better availability. During the process, I clearly mentioned I'm ruling out using Lambda as it has a 1 million free tier which we would exhaust in a day, given you are expecting 1 million per day traffic.

At the end of the interview, the Principal insisted I should have used Lambda and went on to praise Lambda usage. This was my feeling after the interview:

• There are maybe a few incompetent people who don't even understand English and struggle to communicate. I wonder how they get in in the first place.
• They just bluffed any random (1 million) number when you tried to clarify traffic requirements, but don't remember it later on.