C++ Memory Management in Practice

Context

You’re joining a fintech risk engine written in modern C++ that processes millions of transactions per day under strict latency SLOs and regulatory audit requirements. A single memory bug (leak, double-free, use-after-free) can cause process crashes, corrupted risk decisions, or hard-to-reproduce incidents that block releases.

Core Question

Explain your experience with C++ memory management by walking through how you would design, implement, and debug memory ownership in a performance-sensitive service.

Address the following:

1. Ownership & lifetimes: How do you decide who owns an object and how long it should live? Contrast stack vs heap allocation and when each is appropriate.
2. RAII and exception safety: How does RAII prevent leaks, and what does “strong/basic exception safety” mean in practice?
3. Smart pointers: Compare std::unique_ptr, std::shared_ptr, and std::weak_ptr. When is shared_ptr a code smell? How do you avoid cycles?
4. Failure modes & debugging: Describe how you detect and fix leaks, double frees, and use-after-free (tools like ASan/UBSan/Valgrind, core dumps, heap profiling).

Scope Guidance

Assume the interviewer expects implementation-level depth: object layout and allocation, move/copy semantics, destructor behavior, container ownership patterns, and trade-offs between safety and performance. Use a concrete example (e.g., a graph of risk rules, an in-memory cache, or a request pipeline) to demonstrate how you’d apply these principles.