After A sent the resume, someone from the HR department contacted me by email.

They sent me a link to two problems. Whenever you click the link, a timer is launched on their side, and they expect you to send the solutions within two hours.

After this step, there was a technical phone interview which lasted about one hour. It was very technical, covering C++, algorithms, and design.

Then they scheduled a series of phone/Skype/webcam interviews. I had three such interviews during one day, all of which were very technical. They asked me to write code and send it via Skype or email. Again, the focus was on C++, algorithms, and designing distributed, fault-tolerant systems.

Design a large-scale, distributed, and fault-tolerant client-server system.