A plunger (115) of a fuel pump (10) may have an essentially cylindrical base shape for axial movement and rotation within a pump barrel (110) of the fuel pump (10). The plunger (115) may comprise, at a fuel amount controlling end of the plunger (115), an outer surface that comprises a recessed surface region (139), a sealing surface section (165), and a control interface (170, 170A, 170B) connecting in radial direction the recessed surface region (139) with the sealing surface section (165). At the radial inner section of the control interface (170, 170A, 170B), the transition from the recessed surface region (139) to the control interface (170, 170A, 170B) may be curved to thereby reduce or avoid cavitation effects, for example, when used with high water content alternative fuels.