With the rising prevalence of smart mobile phones in our daily life, online ride-hailing platforms have emerged as a viable solution to provide more timely and personalized transportation service, led by such companies as DiDi, Uber, and Lyft.  These platforms also allow idle vehicle vacancy to be more effectively utilized to meet the growing need of on-demand transportation, by connecting potential mobility requests to eligible drivers.  In this talk, we will discuss our train of research on ride-hailing marketplace optimization at DiDi, in particular, order dispatching and driver repositioning.  We will show how value function can be designed to leverage different amount of information and also facilitate knowledge transfer.