A stator-rotor assembly is described, including at least one interface region and a gap between a surface of the stator and a surface of the rotor. The stator is a nozzle or vane that includes circumferential endwalls. Each endwall includes at least one leading edge and one trailing edge, relative to a hot gas flow path. A trailing edge of at least one of the endwalls includes a pattern of cavities that are capable of impeding the entry of hot gas into a wheelspace region that adjoins the gap between the stator and the rotor. The cavities can also be formed on various sections of the rotor. The stator-rotor assembly can be incorporated into various turbomachines, such as gas turbine engines. Related processes are also described.