  In this paper, we present an alternative and elementary proof of a sharp
version of the classical boundary Schwarz lemma by Frolova et al. with initial
proof via analytic semigroup approach and Julia-Carath\'eodory theorem for
univalent holomorphic self-mappings of the open unit disk $\mathbb D\subset
\mathbb C$. Our approach has its extra advantage to get the extremal functions
of the inequality in the boundary Schwarz lemma.
