Call no. 1 - a brief call with the CTO to get to know each other, the role & the company's values and roadmap. The call went smoothly, friendly and overall great.
Call no. 2 - a more technical interview with the CTO:
1. A set of basic questions from the embedded software engineering domain
2. A set of basic questions about the Rust language features
3. A real-time coding task when you have to think out loud and implement a solution to a simple algorithmic problem that should pass a set of predefined unit-tests
Surprisingly though, no questions about the Bitcoin and how it works. Maybe it was redundant to ask this kind of questions in my case since it was already known from the CV that I'm familiar with it.