C++23 std::expected<T, E> provides monadic, value-based error handling. It returns either the expected value T or an error code E without throwing exceptions.

Standard C++ exceptions have zero cost on the happy path, but cost thousands of cycles during stack unwinding on errors. std::expected provides deterministic performance on both success and error paths.

The monadic methods .and_then() and .transform() allow chaining fallible operations like functional pipelines.