Hydrocarbon feedstock containing resid is cracked by a process comprising: (a) heating said hydrocarbon feedstock; (b) mixing the heated hydrocarbon feedstock with steam to form a mixture stream; (c) introducing the mixture stream to a flash/separation apparatus to form i) a vapor phase comprising coke precursors existing as uncoalesced condensate, and ii) a liquid phase; (d) removing the vapor phase as overhead and the liquid phase as bottoms from the flash/separation apparatus; (e) treating the overhead by contacting with a condensing means downstream of the flash/separation apparatus to at least partially coalesce the coke precursors to provide residue hydrocarbon liquid, and subsequently removing the hydrocarbon liquid; (f) heating the treated overhead to provide a heated vapor phase (g) cracking the heated vapor phase in a radiant section of a pyrolysis furnace to produce an effluent comprising olefins, the pyrolysis furnace comprising a radiant section and a convection section; and (h) quenching the effluent and recovering cracked product therefrom. An apparatus for carrying out the process is also provided.