LambdaCDM paradigm is extremely successful at describing the large scale structure formation. However, there is a number of observations suggesting possible deviations from CDM on small scales, such as too-big-to-fail and core-cusp problems. Physically-motivated Warm Dark Matter candidates like Sterile Neutrino WDM could resolve this by introducing small-scale suppression in the Matter Power Spectrum. While the direct measurement of small-scale MPS is challenging, Lyman-alpha absorption spectra of distant quasars provide a proxy to the underlying matter distribution. Interestingly, Lyman-alpha forest Flux Power Spectrum exhibits a cut-off on the scales below ~30 km/s, that could be explained by peculiar velocities, Doppler broadening, physical size of absorbers as well as free-streaming of DM particles. We investigate the origin of the cut-off and implications for searches of DM particle.