In this work, we presented the parallelization strategy and performance benchmarks of the MiMiC-based QM/MM implementation 1 using CPMD and GROMACS as the QM and MM engines, respectively. We detail the technical and algorithmic improvements that allowed our implementation to outperform the existing QM/MM interface in CPMD by roughly an order of magnitude (in terms of wall time per MD time step). Exceptional parallel efficiency is achieved through an efficient parallelization of the QM/MM contributions and by exploiting the highly parallel CPMD and GROMACS packages, both of which run concurrently which is enabled by the loose coupling MPMD approach used in MiMiC.