See also Tyson's php-immutable_cache: https://github.com/TysonAndre/immutable_cache-pecl
Related disucssions: https://github.com/krakjoe/apcu/issues/175 https://github.com/krakjoe/apcu/issues/453 https://github.com/krakjoe/apcu/issues/323 -- Timo Tijhof, Wikimedia Foundation. https://timotijhof.net/
