Unsafe Rust for FFI and low-level optimizations

Unsafe Rust lets you bypass some of the compiler's safety checks when necessary. Common uses include FFI (calling C code), dereferencing raw pointers, and implementing low-level data structures. The unsafe keyword creates a boundary where you promise the code is safe. I minimize unsafe code and encapsulate it in safe APIs. For FFI, I declare external functions with extern "C" and wrap them in safe Rust functions that validate inputs. Unsafe is also used for performance: bypassing bounds checks in tight loops (.get_unchecked()). The key is to isolate unsafe blocks, document invariants, and test thoroughly. When used correctly, unsafe enables zero-cost abstractions that aren't possible in safe Rust.