<p>The design of a reliable system depends greatly on several key factors, including the allocation of reliability to individual components, the use of redundancy, and the allocation of redundant components to enhance overall system reliability. This article proposes a Modified Wild Horse Optimizer (MWHO) for solving system reliability-redundancy allocation problems (RRAPs) with cold-standby redundancy strategy. The cold-standby redundancy is a common technique used to enhance system reliability by adding backup components that remain idle until a failure occurs. However, creating a trade-off between the number of redundant components and their reliabilities with the objective of maximizing overall system reliability remains a challenging problem. Since components can malfunction even when transitioning from standby to active mode, any issues caused by imperfect switching are also taken into account when evaluating the system's performance. The proposed MWHO algorithm incorporates a novel search strategy and a new update mechanism to deal with mixed-integer non-linear RRAPs. The proposed MWHO algorithm is demonstrated to be effective for solving system RRAPs with cold-standby redundancy strategy, outperforming other optimization algorithms in solution quality and convergence speed to yield higher system reliability values. </p>