An apparatus is provided which comprises: a first engine buffer to receive a first engine request; a first engine register coupled to the first engine buffer, wherein the first engine register is to store first engine credits associated with the first engine buffer; a second engine buffer to receive a second engine request; a second engine register coupled to the second engine buffer, wherein the second engine register is to store second engine credits associated with the second engine buffer; and a common buffer which is common to the first and second engines, wherein the first engine credits represents one or more slots in the common buffer for servicing the first engine request for access to a common resource, and wherein the second engine credits represents one or more slots in the common buffer for servicing the second engine request for access to the common resource.