The present disclosure provides a valve seat assembly for a fluid end of a hydraulic fracturing pump. The valve seat assembly includes a valve seat having a substantially cylindrical body defined along an axis. The valve seat has a first seat end and a second seat end with a through bore extending between the first and second seat ends. The cylindrical body has an inner cylinder surface and an exterior cylinder surface with an annular flange formed along the exterior cylinder surface adjacent the first seat end. The through bore expands from a first diameter to a second diameter adjacent the first seat end. The valve seat assembly further includes a leak detection notch formed in the exterior cylinder surface between the annular flange and the second seat end.