# File lib/new_relic/agent/transaction.rb, line 685
      def append_apdex_perf_zone(duration, payload)
        if recording_web_transaction?
          bucket = apdex_bucket(duration, apdex_t)
        elsif background_apdex_t = transaction_specific_apdex_t
          bucket = apdex_bucket(duration, background_apdex_t)
        end

        return unless bucket

        bucket_str = case bucket
        when :apdex_s then APDEX_S
        when :apdex_t then APDEX_T
        when :apdex_f then APDEX_F
        else nil
        end
        payload[:apdex_perf_zone] = bucket_str if bucket_str
      end