On the 787-8, it is a horseshoe service that starts from the aft of left, through the galley upfront then up the right hand side of the aircraft. i.e. Service starts at 5A/D, then proceeds to 1A/D, then to 1D/G and finishing up at 5G/K.
it is on the 787-9 that starts at the same time in both aisles.
Hope this helps.