I applied through other source. The process took 2 months.

Drawn out / repetitive / redundant, overly focused on algorithms you won't use, matches candidates with teams that don't need them. I started interviewing with 2 teams per their process, passed one and failed the other. The team I passed with then filled their role, so they had me interview with a 3rd team but had me start over from first round. I passed this AGAIN (so, to be clear, I've passed 2 out of 3 first rounds with 3 different teams), and then they have me do 2 second round interviews.

I made clear I had a lot of client-side experience with a high degree of skill in interface engineering and client architecture. The system design interview asked me basically to "build WhatsApp," which is a backend distributed architecture problem. They weren't checking that I knew how a REST API works—they wanted to know about database redundancy with sharding and partitioning and so on, interservice data format pros and cons, message broker queue latency, scaling all these backend things. Like, it was not basic stuff. They clearly wanted a distributed systems expert, and of course declined to move forward with my candidacy.

With this being the final result of 5 interviews, I expressed that I felt I was matched with the wrong team and received no reply. Kind of feel like my time was wasted. Also, a portion of people I spoke with had no personality or warmth whatsoever.

Build WhatsApp from a system design perspective.