Tell me about a C++ project you have worked on. What made it challenging?

Note: C++ is chosen for a reason — performance, hardware access, or an existing codebase. Say which one applied, because it frames everything else about the project.

Cover:

• The domain and why C++. Game engine, embedded firmware, trading system, image processing, or a native library behind another language. The reason matters: "we needed deterministic latency under 100 microseconds" tells the interviewer what kind of engineer you are.
• Which C++ you were writing. C++98 with raw pointers is a different job from modern C++17 with smart pointers and move semantics. Be honest — legacy experience is valuable.
• The hard part. Strong candidates: a memory corruption bug that only appeared in release builds, a data race under concurrency, cutting allocation on a hot path, or long compile times you had to attack.
• How you verified the fix. Sanitizers, Valgrind, a benchmark — this is where C++ interviewers judge rigour.