Non-volatile resistive switching (NVRS) has been recently observed with synthesized monolayer molybdenum disulfide (MoS 2 ) as the active layer and termed atomristors . In this paper, we demonstrate the fastest switching speed (<15 ns) among all crystalline two-dimensional (2D) related NVRS devices to the best of our knowledge. For the first time, ab-initio simulation results of atomristors elucidate the mechanism revealing favorable substitution of specific metal ions into sulfur vacancies during switching. This insight combined with area-scaling experimental studies indicate a local conductive-bridge-like nature. The proposed mechanism is further supported by sulfur annealing recovery phenomenon. Moreover, exfoliated MoS 2 monolayer is demonstrated to have memory effect for the first time, expanding the materials beyond synthesized films. State-of-the-art non-volatile RF switches based on MoS 2 atomristors were prepared, featuring 0.25 dB insertion loss, 29 dB isolation (both at 67 GHz), and 70 THz cutoff frequency, a record performance compared to emerging RF switches. Our pioneering work suggests that memory effect maybe present in dozens or 100s of 2D monolayers similar to MoS 2 paving the path for new scientific studies for understanding the rich physics, and engineering research towards diverse device applications.