1. Phone conversation with recruiter.
2. In-person interview with hiring manager (they call it a coffee chat).
3. Technical phone screen.
4. Coding challenge (5-15 hours).
5. In-person full-day interview (~6 hours).

After the final on-site interview, the hiring manager informed me that they need engineers who have strong expertise in the specific APIs/technologies that they use internally within their teams. I do not understand why they wasted my time, when I or my resume never mentioned that I had strong expertise in the technologies that they use.

Their whole focus is on the APIs and frameworks that they internally use within their teams. They need experts who have deep knowledge of the APIs they use, rather than people who have an ability to learn and implement. Not even a single interviewer cared or asked about my area of expertise and what I am doing currently.

Ex:

1. Design a New Relic agent.
2. Design a session about fixing some of their sample problems they are facing at New Relic.
3. Peer-programming with their engineers about some of their ongoing tasks/tickets. They expect that you know the specifics and low-level details of their APIs in this session.