A furnace for performing an endothermic process comprises tubes containing a catalyst for converting a gaseous feed, said tubes positioned inside the furnace, inner burners mounted to a furnace roof between the tubes, and outer burners mounted to the furnace roof between the tubes and a furnace wall. The outer burners are positioned close to the furnace wall, and configured to operate with 45-60% of the power of the inner burners and with an inlet velocity between 90 to 110% of the inlet velocity of the inner burners.