Current-induced spin-transfer torques (STT) and spin-orbit torques (SOT) enable the electrical switching of magnetic tunnel junctions (MTJs) in nonvolatile magnetic random access memories. In order to develop faster memory devices, an improvement of the timescales underlying the currentdriven magnetization dynamics is required. Here we report all-electrical time-resolved measurements of magnetization reversal driven by SOT in a three-terminal MTJ device. Single-shot measurements of the MTJ resistance during current injection reveal that SOT switching involves a stochastic two-step process consisting of a domain nucleation time and propagation time, which have different genesis, timescales, and statistical distributions compared to STT switching. We further show that the combination of SOT, STT, and voltage control of magnetic anisotropy (VCMA) leads to reproducible sub-ns switching with a spread of the cumulative switching time smaller than 0.2 ns. Our measurements unravel the combined impact of SOT, STT, and VCMA in determining the switching speed and efficiency of MTJ devices. Switching nanomagnets by current injection offers unparalleled scalability, as well as low power and high speed operation compared to control via external magnetic fields 1-3. Spin-transfer torques (STT) 1,4 are presently employed in memory and spin logic applications 5,6 to control the state of magnetic tunnel junctions (MTJ) via an electric current passing through the reference and free magnetic layers, which allows also for efficient readout of the MTJ through the tunnel magnetoresistance (TMR). Time-resolved studies of magnetization reversal in spin valve 7,8 and MTJ devices 9-12 have shown that STT enables switching on a timescale of 100 to 1 ns, depending on the driving current 13 and external field 14. However, STT switching is characterized by nonreproducible dynamic paths and incubation times up to several tens of ns long, which limit the reliability and speed of the reversal process to about 10-20 ns, even when mitigation strategies based on large driving currents or noncollinear spin injection are employed 13,15,16. These limitations may be overcome by magnetization reversal driven by spin-orbit torques (SOT) 3,17-19 , which has been recently demonstrated in three-terminal MTJs with in-plane 20,21 as well as out-of-plane magnetization 22-25. SOT switching combines an in-plane current injection geometry with charge-to-spin conversion due to the spin Hall effect and interfacial spin scattering 3. Such a geometry decouples the write and read current paths, improving the MTJ endurance and operation speed by minimizing electrical stress of the tunnel barrier and allowing for tuning the barrier thickness for high TMR, fast read-out, and minimal read disturbances. Moreover, in devices with perpendicular magnetization, the injected spin current is orthogonal to the quiescent magnetization of the free layer, thus providing an "instant on" torque that is expected to minimize the switching incubation time 25-27 .