What would be the fastest way to parse a Json String to a multidimensional array in C++?

Question

I am currently using the JsonCPP library but it is proving be a bit slow for my needs. Appreciate your thoughts on this!

            json_response = response.extract_json().get();
            auto json = json_response.serialize();
            std::string res(json.begin(), json.end());
            //String to array
            auto arrayJson = json_response.at(U("loans")).as_array();