Nowadays, the performance of data-center networks (DCNs) has become crucial for advancing large-scale computing applications. Hence, to improve the throughput, energy-efficiency and latency of DCNs, people are trying to replace the electrical packet switching (EPS) based spine switches with optical circuit switching (OCS) based ones. In an OCS-based DCN, topology engineering (TPE) is the key operation to dynamically reconfigure its inter-pod topology for accommodating traffic with optimized resource utilization. TPE consists of two highly-correlated steps, i.e., optimizing the target physical inter-pod topology of the DCN based on a traffic matrix, and planning the procedure of OCS reconfiguration such that hitless transition can be achieved. In this paper, we study how to optimize the two steps jointly to efficiently accelerate the hitless reconfiguration of an OCS-based DCN. We formulate a mixed linear programming model (MILP) to solve the joint optimization exactly. Then, to solve the problem time-efficiently, we propose an approach that optimizes TPE design greedily according to various metrics to minimize the number of stages required in hitless reconfiguration for TPE. Extensive simulations verify the effectiveness of our proposals and demonstrate their benefits over existing benchmark.