Otimização de Consulta

[jacksonihs 0]

Minha consulta está muito demorada, alguém tem alguma ideia de como melhorar, creio que o segundo select está piorando o processo, rsrsrs...
                $consumption = $this->reading

                ->selectRaw('apartments.condominium_id, 

                condominiums.name, 

                apartments.number, 

                apartments.block,

                    readings.reading as reading, 

                    readings.reading/1000 as reading_m3, 

                    DATE_FORMAT(readings.readed_at, "%d/%m/%Y") as date,

                    DATE_FORMAT(readings.readed_at, "%H:%i") as hour, 

                    IFNULL(readings.reading/1000 - 

                    (select rd.reading/1000 from readings rd where rd.id < readings.id and rd.meter_id = readings.meter_id 

                        order by rd.readed_at desc limit 0,1),0) as consumption, 

                    readings.readed_at as readed_at, 

                    readings.meter_leak, 

                    readings.meter_wire_cut, 

                    readings.meter_id, 

                    meters.meter_number, 

                    meters.transmitter_number, 

                    meter_types.type')

                ->join('meters', 'readings.meter_id', '=', 'meters.id')

                ->join('meter_types', 'meters.meter_type_id', 'meter_types.id')

                ->join('apartments', 'meters.apartment_id', '=', 'apartments.id')

                ->join('condominiums', 'condominiums.id', '=', 'apartments.condominium_id')

                ->where('condominiums.id', '=', $id)

                ->whereBetween('readings.readed_at', [$dateStart, $dateEnd])

                ->orderBy('meters.meter_number', 'asc')

                ->orderBy('readings.readed_at', 'asc')

                ->get();