I attended walk-in interview.
Two rounds were conducted one in person and one virtual round.
In both rounds questions are constructors, destructors, copy assignment, copy constructor, basics of STL, smart pointers, mutex, semaphore, basics about threads, storage containers, virtual functions, vtable, OOPS, run time polymorphism, overriding, overloading, deadlock, static vs global.
There was third round from client asked to explain architecture of current project, asked to implement factory pattern, singleton pattern and design a class to make led blink.